Software testing Q and A

1. What is black box/white box testing?

Black-box and white-box are test design methods. Black-box test design treats the system as a “black-box”, so it doesn’t explicitly use knowledge of the internal structure. Black-box test design is usually described as focusing on testing functional requirements. Synonyms for black-box include: behavioral, functional, opaque-box, and closed-box. White-box test design allows one to peek inside the “box”, and it focuses specifically on using internal knowledge of the software to guide the selection of test data. Synonyms for white-box include: structural, glass-box and clear-box.

While black-box and white-box are terms that are still in popular use, many people prefer the terms “behavioral” and “structural”. Behavioral test design is slightly different from black-box test design because the use of internal knowledge isn’t strictly forbidden, but it’s still discouraged. In practice, it hasn’t proven useful to use a single test design method. One has to use a mixture of different methods so that they aren’t hindered by the limitations of a particular one. Some call this “gray-box” or “translucent-box” test design, but others wish we’d stop talking about boxes altogether.

It is important to understand that these methods are used during the test design phase, and their influence is hard to see in the tests once they’re implemented. Note that any level of testing (unit testing, system testing, etc.) can use any test design methods. Unit testing is usually associated with structural test design, but this is because testers usually don’t have well-defined requirements at the unit level to validate.

2. What are unit, component and integration testing?

Note that the definitions of unit, component, integration, and integration testing are recursive:

Unit. The smallest compliable component. A unit typically is the work of one programmer (At least in principle). As defined, it does not include any called sub-components (for procedural languages) or communicating components in general.

Unit Testing: in unit testing called components (or communicating components) are replaced with stubs, simulators, or trusted components. Calling components are replaced with drivers or trusted super-components. The unit is tested in isolation.

component: a unit is a component. The integration of one or more components is a component.

Note: The reason for “one or more” as contrasted to “Two or more” is to allow for components that call themselves recursively.

component testing: same as unit testing except that all stubs and simulators are replaced with the real thing.

Two components (actually one or more) are said to be integrated when:

a. They have been compiled, linked, and loaded together.
b. They have successfully passed the integration tests at the interface between them.

Thus, components A and B are integrated to create a new, larger, component (A,B). Note that this does not conflict with the idea of incremental integration—it just means that A is a big component and B, the component added, is a small one.

Integration testing: carrying out integration tests.

Integration tests (After Leung and White) for procedural languages. This is easily generalized for OO languages by using the equivalent constructs for message passing. In the following, the word “call” is to be understood in the most general sense of a data flow and is not restricted to just formal subroutine calls and returns – for example, passage of data through global data structures and/or the use of pointers.

Let A and B be two components in which A calls B.
Let Ta be the component level tests of A
Let Tb be the component level tests of B
Tab The tests in A’s suite that cause A to call B.
Tbsa The tests in B’s suite for which it is possible to sensitize A — the inputs
are to A, not B.
Tbsa + Tab == the integration test suite (+ = union).

Note: Sensitize is a technical term. It means inputs that will cause a routine to go down a specified path. The inputs are to A. Not every input to A will cause A to traverse a path in which B is called. Tbsa is the set of tests which do cause A to follow a path in which B is called. The outcome of the test of B may or may not be affected.

There have been variations on these definitions, but the key point is that it is pretty darn formal and there’s a goodly hunk of testing theory, especially as concerns integration testing, OO testing, and regression testing, based on them.

As to the difference between integration testing and system testing. System testing specifically goes after behaviors and bugs that are properties of the entire system as distinct from properties attributable to components (unless, of course, the component in question is the entire system). Examples of system testing issues:
Resource loss bugs, throughput bugs, performance, security, recovery,
Transaction synchronization bugs (often misnamed “timing bugs”).

3. What’s the difference between load and stress testing ?

One of the most common, but unfortunate misuse of terminology is treating “load testing” and “stress testing” as synonymous. The consequence of this ignorant semantic abuse is usually that the system is neither properly “load tested” nor subjected to a meaningful stress test.

Stress testing is subjecting a system to an unreasonable load while denying it the resources (e.g., RAM, disc, mips, interrupts, etc.) needed to process that load. The idea is to stress a system to the breaking point in order to find bugs that will make that break potentially harmful. The system is not expected to process the overload without adequate resources, but to behave (e.g., fail) in a decent manner (e.g., not corrupting or losing data). Bugs and failure modes discovered under stress testing may or may not be repaired depending on the application, the failure mode, consequences, etc. The load (incoming transaction stream) in stress testing is often deliberately distorted so as to force the system into resource depletion.

Load testing is subjecting a system to a statistically representative (usually) load. The two main reasons for using such loads is in support of software reliability testing and in performance testing. The term “load testing” by itself is too vague and imprecise to warrant use. For example, do you mean representative load,” “overload,” “high load,” etc. In performance testing, load is
varied from a minimum (zero) to the maximum level the system can sustain without running out of resources or having, transactions >suffer (application-specific) excessive delay.

A third use of the term is as a test whose objective is to determine the maximum sustainable load the system can handle. In this usage, “load testing” is merely testing at the highest transaction arrival rate in performance testing.

4. What’s the difference between QA and testing?

QA is more a preventive thing, ensuring quality in the company and therefore the product rather than just testing the product for software bugs?

TESTING means “quality control”
QUALITY CONTROL measures the quality of a product
QUALITY ASSURANCE measures the quality of processes used to create a
quality product.

6. What is Software Quality Assurance?

Software QA involves the entire software development PROCESS – monitoring and improving the process, making sure that any agreed-upon standards and procedures are followed, and ensuring that problems are found and dealt with. It is oriented to ‘prevention’.

7. What is Software Testing?
Testing involves operation of a system or application under controlled conditions and evaluating the results (eg, ‘if the user is in interface A of the application while using hardware B, and does C, then D should happen’). The controlled conditions should include both normal and abnormal conditions. Testing should intentionally attempt to make things go wrong to determine if things happen when they shouldn’t or things don’t happen when they should. It is oriented to ‘detection’.

Organizations vary considerably in how they assign responsibility for QA and testing. Sometimes they’re the combined responsibility of one group or individual. Also common are project teams that include a mix of testers and developers who work closely together, with overall QA processes monitored by project managers. It will depend on what best fits an organization’s size and business structure.

8. What are some recent major computer system failures caused by Software bugs?

  •  In March of 2002 it was reported that software bugs in Britain’s national tax system resulted in more than 100,000 erroneous tax overcharges. The problem was partly attibuted to the difficulty of testing the integration of multiple systems.
  • A newspaper columnist reported in July 2001 that a serious flaw was found in off-the-shelf software that had long been used in systems for tracking certain U.S. nuclear materials. The same software had been recently donated to another country to be used in tracking their own nuclear materials, and it was not until scientists in that country discovered the problem, and shared the information, that U.S. officials became aware of the problems.
  • According to newspaper stories in mid-2001, a major systems development contractor was fired and sued over problems with a large retirement plan management system. According to the reports, the client claimed that system deliveries were late, the software had excessive defects, and it caused other systems to crash.
  • In January of 2001 newspapers reported that a major European railroad was hit by the aftereffects of the Y2K bug. The company found that many of their newer trains would not run due to their inability to recognize the date ’31/12/2000′; the trains were started by altering the control system’s date settings.
  • News reports in September of 2000 told of a software vendor settling a lawsuit with a large mortgage lender; the vendor had reportedly delivered an online mortgage processing system that did not meet specifications, was delivered late, and didn’t work.
  • In early 2000, major problems were reported with a new computer system in a large suburban U.S. public school district with 100,000+ students; problems included 10,000 erroneous report cards and students left stranded by failed class registration systems; the district’s CIO was fired. The school district decided to reinstate it’s original 25-year old system for at least a year until the bugs were worked out of the new system by the software vendors.
  •  In October of 1999 the $125 million NASA Mars Climate Orbiter spacecraft was believed to be lost in space due to a simple data conversion error. It was determined that spacecraft software used certain data in English units that should have been in metric units. Among other tasks, the orbiter was to serve as a communications relay for the Mars Polar Lander mission, which failed for unknown reasons in December 1999. Several investigating panels were convened to determine the process failures that allowed the error to go undetected.
  • Bugs in software supporting a large commercial high-speed data network affected 70,000 business customers over a period of 8 days in August of 1999. Among those affected was the electronic trading system of the largest U.S. futures exchange, which was shut down for most of a week as a result of the outages.
  • In April of 1999 a software bug caused the failure of a $1.2 billion military satellite launch, the costliest unmanned accident in the history of Cape Canaveral launches. The failure was the latest in a string of launch failures, triggering a complete military and industry review of U.S. space launch programs, including software integration and testing processes. Congressional oversight hearings were requested.
  • A small town in Illinois received an unusually large monthly electric bill of $7 million in March of 1999. This was about 700 times larger than its normal bill. It turned out to be due to bugs in new software that had been purchased by the local power company to deal with Y2K software issues.
  • In early 1999 a major computer game company recalled all copies of a popular new product due to software problems. The company made a public apology for releasing a product before it was ready.
  • The computer system of a major online U.S. stock trading service failed during trading hours several times over a period of days in February of 1999 according to nationwide news reports. The problem was reportedly due to bugs in a software upgrade intended to speed online trade confirmations.
  • In April of 1998 a major U.S. data communications network failed for 24 hours, crippling a large part of some U.S. credit card transaction authorization systems as well as other large U.S. bank, retail, and government data systems. The cause was eventually traced to a software bug.
  • January 1998 news reports told of software problems at a major U.S. telecommunications company that resulted in no charges for long distance calls for a month for 400,000 customers. The problem went undetected until customers called up with questions about their bills.
  • In November of 1997 the stock of a major health industry company dropped 60% due to reports of failures in computer billing systems, problems with a large database conversion, and inadequate software testing. It was reported that more than $100,000,000 in receivables had to be written off and that multi-million dollar fines were levied on the company by government agencies.
  • A retail store chain filed suit in August of 1997 against a transaction processing system vendor (not a credit card company) due to the software’s inability to handle credit cards with year 2000 expiration dates.
  • In August of 1997 one of the leading consumer credit reporting companies reportedly shut down their new public web site after less than two days of operation due to software problems. The new site allowed web site visitors instant access, for a small fee, to their personal credit reports. However, a number of initial users ended up viewing each others’ reports instead of their own, resulting in irate customers and nationwide publicity. The problem was attributed to “…unexpectedly high demand from consumers and faulty software that routed the files to the wrong computers.”
  • In November of 1996, newspapers reported that software bugs caused the 411 telephone information system of one of the U.S. RBOC’s to fail for most of a day. Most of the 2000 operators had to search through phone books instead of using their 13,000,000-listing database. The bugs were introduced by new software modifications and the problem software had been installed on both the production and backup systems. A spokesman for the software vendor reportedly stated that ‘It had nothing to do with the integrity of the software. It was human error.’
  • On June 4 1996 the first flight of the European Space Agency’s new Ariane 5 rocket failed shortly after launching, resulting in an estimated uninsured loss of a half billion dollars. It was reportedly due to the lack of exception handling of a floating-point error in a conversion from a 64-bit integer to a 16-bit signed integer.
  • Software bugs caused the bank accounts of 823 customers of a major U.S. bank to be credited with $924,844,208.32 each in May of 1996, according to newspaper reports. The American Bankers Association claimed it was the largest such error in banking history. A bank spokesman said the programming errors were corrected and all funds were recovered.
  • Software bugs in a Soviet early-warning monitoring system nearly brought on nuclear war in 1983, according to news reports in early 1999. The software was supposed to filter out false missile detections caused by Soviet satellites picking up sunlight reflections off cloud-tops, but failed to do so. Disaster was averted when a Soviet commander, based on a what he said was a ‘…funny feeling in my gut’, decided the apparent missile attack was a false alarm. The filtering software code was rewritten.

9. Why is it often hard for management to get serious about quality assurance?

Solving problems is a high-visibility process; preventing problems is low-visibility. This is illustrated by an old parable:
In ancient China there was a family of healers, one of whom was known throughout the land and employed as a physician to a great lord. The physician was asked which of his family was the most skillful healer. He replied,
“I tend to the sick and dying with drastic and dramatic treatments, and on occasion someone is cured and my name gets out among the lords.”
“My elder brother cures sickness when it just begins to take root, and his skills are known among the local peasants and neighbors.”
“My eldest brother is able to sense the spirit of sickness and eradicate it before it takes form. His name is unknown outside our home.”

10. Why does Software have bugs?

  • Miscommunication or no communication – as to specifics of what an application should or shouldn’t do (the application’s requirements).
  • Software complexity – the complexity of current software applications can be difficult to comprehend for anyone without experience in modern-day software development. Windows-type interfaces, client-server and distributed applications, data communications, enormous relational databases, and sheer size of applications have all contributed to the exponential growth in software/system complexity. And the use of object-oriented techniques can complicate instead of simplify a project unless it is well-engineered.
  • Programming errors – programmers, like anyone else, can make mistakes.
  • changing requirements – the customer may not understand the effects of changes, or may understand and request them anyway – redesign, rescheduling of engineers, effects on other projects, work already completed that may have to be redone or thrown out, hardware requirements that may be affected, etc. If there are many minor changes or any major changes, known and unknown dependencies among parts of the project are likely to interact and cause problems, and the complexity of keeping track of changes may result in errors. Enthusiasm of engineering staff may be affected. In some fast-changing business environments, continuously modified requirements may be a fact of life. In this case, management must understand the resulting risks, and QA and test engineers must adapt and plan for continuous extensive testing to keep the inevitable bugs from running out of control.
  • time pressures – scheduling of software projects is difficult at best, often requiring a lot of guesswork. When deadlines loom and the crunch comes, mistakes will be made.
    egos – people prefer to say things like:
    ‘no problem’
    ‘piece of cake’
    ‘I can whip that out in a few hours’
    ‘it should be easy to update that old code’

instead of:
‘that adds a lot of complexity and we could end up
making a lot of mistakes’
‘we have no idea if we can do that; we’ll wing it’
‘I can’t estimate how long it will take, until I
take a close look at it’
‘we can’t figure out what that old spaghetti code
did in the first place’

If there are too many unrealistic ‘no problem’s’, the result is bugs.

  • poorly documented code – it’s tough to maintain and modify code that is badly written or poorly documented; the result is bugs. In many organizations management provides no incentive for programmers to document their code or write clear, understandable code. In fact, it’s usually the opposite: they get points mostly for quickly turning out code, and there’s job security if nobody else can understand it (‘if it was hard to write, it should be hard to read’).
  • software development tools – visual tools, class libraries, compilers, scripting tools, etc. often introduce their own bugs or are poorly documented, resulting in added bugs.

11. How can new Software QA processes be introduced in an existing organization?

  • A lot depends on the size of the organization and the risks involved. For large organizations with high-risk (in terms of lives or property) projects, serious management buy-in is required and a formalized QA process is necessary.
  • Where the risk is lower, management and organizational buy-in and QA implementation may be a slower, step-at-a-time process. QA processes should be balanced with productivity so as to keep bureaucracy from getting out of hand.
  • For small groups or projects, a more ad-hoc process may be appropriate, depending on the type of customers and projects. A lot will depend on team leads or managers, feedback to developers, and ensuring adequate communications among customers, managers, developers, and testers.
  • In all cases the most value for effort will be in requirements management processes, with a goal of clear, complete, testable requirement specifications or expectations.

12. What is verification? validation?

Verification typically involves reviews and meetings to evaluate documents, plans, code, requirements, and specifications. This can be done with checklists, issues lists, walkthroughs, and inspection meetings. Validation typically involves actual testing and takes place after verifications are completed. The term ‘IV & V’ refers to Independent Verification and Validation.

13. What is a ‘walkthrough’?

A ‘walkthrough’ is an informal meeting for evaluation or informational purposes. Little or no preparation is usually required.

14. What’s an ‘inspection’?

An inspection is more formalized than a ‘walkthrough’, typically with 3-8 people including a moderator, reader, and a recorder to take notes. The subject of the inspection is typically a document such as a requirements spec or a test plan, and the purpose is to find problems and see what’s missing, not to fix anything. Attendees should prepare for this type of meeting by reading thru the document; most problems will be found during this preparation. The result of the inspection meeting should be a written report. Thorough preparation for inspections is difficult, painstaking work, but is one of the most cost effective methods of ensuring quality. Employees who are most skilled at inspections are like the ‘eldest brother’ in the parable in ‘Why is it often hard for management to get serious about quality assurance?’. Their skill may have low visibility but they are extremely valuable to any software development organization, since bug prevention is far more cost-effective than bug detection.

15. What kinds of testing should be considered?

  • Black box testing – not based on any knowledge of internal design or code. Tests are based on requirements and functionality.
  • White box testing – based on knowledge of the internal logic of an application’s code. Tests are based on coverage of code statements, branches, paths, conditions.
  • unit testing – the most ‘micro’ scale of testing; to test particular functions or code modules. Typically done by the programmer and not by testers, as it requires detailed knowledge of the internal program design and code. Not always easily done unless the application has a well-designed architecture with tight code; may require developing test driver modules or test harnesses.
  • incremental integration testing – continuous testing of an application as new functionality is added; requires that various aspects of an application’s functionality be independent enough to work separately before all parts of the program are completed, or that test drivers be developed as needed; done by programmers or by testers.
  • integration testing – testing of combined parts of an application to determine if they function together correctly. The ‘parts’ can be code modules, individual applications, client and server applications on a network, etc. This type of testing is especially relevant to client/server and distributed systems.
  • functional testing – black-box type testing geared to functional requirements of an application; this type of testing should be done by testers. This doesn’t mean that the programmers shouldn’t check that their code works before releasing it (which of course applies to any stage of testing.)
  • system testing – black-box type testing that is based on overall requirements specifications; covers all combined parts of a system.
  • end-to-end testing – similar to system testing; the ‘macro’ end of the test scale; involves testing of a complete application environment in a situation that mimics real-world use, such as interacting with a database, using network communications, or interacting with other hardware, applications, or systems if appropriate.
  • sanity testing – typically an initial testing effort to determine if a new software version is performing well enough to accept it for a major testing effort. For example, if the new software is crashing systems every 5 minutes, bogging down systems to a crawl, or destroying databases, the software may not be in a ‘sane’ enough condition to warrant further testing in its current state.
  • regression testing – re-testing after fixes or modifications of the software or its environment. It can be difficult to determine how much re-testing is needed, especially near the end of the development cycle. Automated testing tools can be especially useful for this type of testing.
  • acceptance testing – final testing based on specifications of the end-user or customer, or based on use by end-users/customers over some limited period of time.
  • load testing – testing an application under heavy loads, such as testing of a web site under a range of loads to determine at what point the system’s response time degrades or fails.
  • stress testing – term often used interchangeably with ‘load’ and ‘performance’ testing. Also used to describe such tests as system functional testing while under unusually heavy loads, heavy repetition of certain actions or inputs, input of large numerical values, large complex queries to a database system, etc.
  • performance testing – term often used interchangeably with ‘stress’ and ‘load’ testing. Ideally ‘performance’ testing (and any other ‘type’ of testing) is defined in requirements documentation or QA or Test Plans.
  • usability testing – testing for ‘user-friendliness’. Clearly this is subjective, and will depend on the targeted end-user or customer. User interviews, surveys, video recording of user sessions, and other techniques can be used. Programmers and testers are usually not appropriate as usability testers.
  • install/uninstall testing – testing of full, partial, or upgrade install/uninstall processes.
  • recovery testing – testing how well a system recovers from crashes, hardware failures, or other catastrophic problems.
  • security testing – testing how well the system protects against unauthorized internal or external access, willful damage, etc; may require sophisticated testing techniques.
  • compatability testing – testing how well software performs in a particular hardware/software/operating system/network/etc. environment.
  • exploratory testing – often taken to mean a creative, informal software test that is not based on formal test plans or test cases; testers may be learning the software as they test it.
  • ad-hoc testing – similar to exploratory testing, but often taken to mean that the testers have significant understanding of the software before testing it.
  • user acceptance testing – determining if software is satisfactory to an end-user or customer.
  • comparison testing – comparing software weaknesses and strengths to competing products.
  • alpha testing – testing of an application when development is nearing completion; minor design changes may still be made as a result of such testing. Typically done by end-users or others, not by programmers or testers.
  • beta testing – testing when development and testing are essentially completed and final bugs and problems need to be found before final release. Typically done by end-users or others, not by programmers or testers.
  • mutation testing – a method for determining if a set of test data or test cases is useful, by deliberately introducing various code changes (‘bugs’) and retesting with the original test data/cases to determine if the ‘bugs’ are detected. Proper implementation requires large computational resources.

16. What are 5 common problems in the software development process?

  • poor requirements – if requirements are unclear, incomplete, too general, or not testable, there will be problems.
  • unrealistic schedule – if too much work is crammed in too little time, problems are inevitable.
  • inadequate testing – no one will know whether or not the program is any good until the customer complains or systems crash.
  • featuritis – requests to pile on new features after development is underway; extremely common.
  • miscommunication – if developers don’t know what’s needed or customer’s have erroneous expectations, problems are guaranteed.

17. What are 5 common solutions to software development problems?
 solid requirements – clear, complete, detailed, cohesive, attainable, testable requirements that are agreed to by all players. Use prototypes to help nail down requirements.
 realistic schedules – allow adequate time for planning, design, testing, bug fixing, re-testing, changes, and documentation; personnel should be able to complete the project without burning out.
 adequate testing – start testing early on, re-test after fixes or changes, plan for adequate time for testing and bug-fixing.
 stick to initial requirements as much as possible – be prepared to defend against changes and additions once development has begun, and be prepared to explain consequences. If changes are necessary, they should be adequately reflected in related schedule changes. If possible, use rapid prototyping during the design phase so that customers can see what to expect. This will provide them a higher comfort level with their requirements decisions and minimize changes later on.
 communication – require walkthroughs and inspections when appropriate; make extensive use of group communication tools – e-mail, groupware, networked bug-tracking tools and change management tools, intranet capabilities, etc.; insure that documentation is available and up-to-date – preferably electronic, not paper; promote teamwork and cooperation; use prototypes early on so that customers’ expectations are clarified.

18. What is software ‘quality’?

Quality software is reasonably bug-free, delivered on time and within budget, meets requirements and/or expectations, and is maintainable. However, quality is obviously a subjective term. It will depend on who the ‘customer’ is and their overall influence in the scheme of things. A wide-angle view of the ‘customers’ of a software development project might include end-users, customer acceptance testers, customer contract officers, customer management, the development organization’s management/accountants/testers/salespeople, future software maintenance engineers, stockholders, magazine columnists, etc. Each type of ‘customer’ will have their own slant on ‘quality’ – the accounting department might define quality in terms of profits while an end-user might define quality as user-friendly and bug-free.

19. What is ‘good code’?

‘Good code’ is code that works, is bug free, and is readable and maintainable. Some organizations have coding ‘standards’ that all developers are supposed to adhere to, but everyone has different ideas about what’s best, or what is too many or too few rules. There are also various theories and metrics, such as McCabe Complexity metrics. It should be kept in mind that excessive use of standards and rules can stifle productivity and creativity. ‘Peer reviews’, ‘buddy checks’ code analysis tools, etc. can be used to check for problems and enforce standards.
For C and C++ coding, here are some typical ideas to consider in setting rules/standards; these may or may not apply to a particular situation:
 minimize or eliminate use of global variables.
 use descriptive function and method names – use both upper and lower case, avoid abbreviations, use as many characters as necessary to be adequately descriptive (use of more than 20 characters is not out of line); be consistent in naming conventions.
 use descriptive variable names – use both upper and lower case, avoid abbreviations, use as many characters as necessary to be adequately descriptive (use of more than 20 characters is not out of line); be consistent in naming conventions.
 function and method sizes should be minimized; less than 100 lines of code is good, less than 50 lines is preferable.
 function descriptions should be clearly spelled out in comments preceding a function’s code.
 organize code for readability.
 use whitespace generously – vertically and horizontally
 each line of code should contain 70 characters max.
 one code statement per line.
 coding style should be consistent throught a program (eg, use of brackets, indentations, naming conventions, etc.)
 in adding comments, err on the side of too many rather than too few comments; a common rule of thumb is that there should be at least as many lines of comments (including header blocks) as lines of code.
 no matter how small, an application should include documentaion of the overall program function and flow (even a few paragraphs is better than nothing); or if possible a separate flow chart and detailed program documentation.
 make extensive use of error handling procedures and status and error logging.
 for C++, to minimize complexity and increase maintainability, avoid too many levels of inheritance in class heirarchies (relative to the size and complexity of the application). Minimize use of multiple inheritance, and minimize use of operator overloading (note that the Java programming language eliminates multiple inheritance and operator overloading.)
 for C++, keep class methods small, less than 50 lines of code per method is preferable.
 for C++, make liberal use of exception handlers

20. What is ‘good design’?
‘Design’ could refer to many things, but often refers to ‘functional design’ or ‘internal design’. Good internal design is indicated by software code whose overall structure is clear, understandable, easily modifiable, and maintainable; is robust with sufficient error-handling and status logging capability; and works correctly when implemented. Good functional design is indicated by an application whose functionality can be traced back to customer and end-user requirements. For programs that have a user interface, it’s often a good idea to assume that the end user will have little computer knowledge and may not read a user manual or even the on-line help; some common rules-of-thumb include:
 the program should act in a way that least surprises the user
 it should always be evident to the user what can be done next and how to exit
 the program shouldn’t let the users do something stupid without warning them.

21. What is SEI? CMM? ISO? IEEE? ANSI? Will it help?
 SEI = ‘Software Engineering Institute’ at Carnegie-Mellon University; initiated by the U.S. Defense Department to help improve software development processes.
 CMM = ‘Capability Maturity Model’, developed by the SEI. It’s a model of 5 levels of organizational ‘maturity’ that determine effectiveness in delivering quality software. It is geared to large organizations such as large U.S. Defense Department contractors. However, many of the QA processes involved are appropriate to any organization, and if reasonably applied can be helpful. Organizations can receive CMM ratings by undergoing assessments by qualified auditors.
Level 1 – characterized by chaos, periodic panics, and heroic
efforts required by individuals to successfully
complete projects. Few if any processes in place;
successes may not be repeatable.

Level 2 – software project tracking, requirements management,
realistic planning, and configuration management
processes are in place; successful practices can
be repeated.

Level 3 – standard software development and maintenance processes
are integrated throughout an organization; a Software
Engineering Process Group is is in place to oversee
software processes, and training programs are used to
ensure understanding and compliance.

Level 4 – metrics are used to track productivity, processes,
and products. Project performance is predictable,
and quality is consistently high.

Level 5 – the focus is on continouous process improvement. The
impact of new processes and technologies can be
predicted and effectively implemented when required.

Perspective on CMM ratings: During 1997-2001, 1018 organizations
were assessed. Of those, 27% were rated at Level 1, 39% at 2,
23% at 3, 6% at 4, and 5% at 5. (For ratings during the period
1992-96, 62% were at Level 1, 23% at 2, 13% at 3, 2% at 4, and
0.4% at 5.) The median size of organizations was 100 software
engineering/maintenance personnel; 32% of organizations were
U.S. federal contractors or agencies. For those rated at
Level 1, the most problematical key process area was in
Software Quality Assurance.
 ISO = ‘International Organisation for Standardization’ – The ISO 9001:2000 standard (which replaces the previous standard of 1994) concerns quality systems that are assessed by outside auditors, and it applies to many kinds of production and manufacturing organizations, not just software. It covers documentation, design, development, production, testing, installation, servicing, and other processes. The full set of standards consists of: (a)Q9001-2000 – Quality Management Systems: Requirements; (b)Q9000-2000 – Quality Management Systems: Fundamentals and Vocabulary; (c)Q9004-2000 – Quality Management Systems: Guidelines for Performance Improvements. To be ISO 9001 certified, a third-party auditor assesses an organization, and certification is typically good for about 3 years, after which a complete reassessment is required. Note that ISO certification does not necessarily indicate quality products – it indicates only that documented processes are followed.
 IEEE = ‘Institute of Electrical and Electronics Engineers’ – among other things, creates standards such as ‘IEEE Standard for Software Test Documentation’ (IEEE/ANSI Standard 829), ‘IEEE Standard of Software Unit Testing (IEEE/ANSI Standard 1008), ‘IEEE Standard for Software Quality Assurance Plans’ (IEEE/ANSI Standard 730), and others.
 ANSI = ‘American National Standards Institute’, the primary industrial standards body in the U.S.; publishes some software-related standards in conjunction with the IEEE and ASQ (American Society for Quality).
 Other software development process assessment methods besides CMM and ISO 9000 include SPICE, Trillium, TickIT. and Bootstrap.

22. What is the ‘software life cycle’?

The life cycle begins when an application is first conceived and ends when it is no longer in use. It includes aspects such as initial concept, requirements analysis, functional design, internal design, documentation planning, test planning, coding, document preparation, integration, testing, maintenance, updates, retesting, phase-out, and other aspects.

23. Will automated testing tools make testing easier?
 Possibly. For small projects, the time needed to learn and implement them may not be worth it. For larger projects, or on-going long-term projects they can be valuable.
 A common type of automated tool is the ‘record/playback’ type. For example, a tester could click through all combinations of menu choices, dialog box choices, buttons, etc. in an application GUI and have them ‘recorded’ and the results logged by a tool. The ‘recording’ is typically in the form of text based on a scripting language that is interpretable by the testing tool. If new buttons are added, or some underlying code in the application is changed, etc. the application can then be retested by just ‘playing back’ the ‘recorded’ actions, and comparing the logging results to check effects of the changes. The problem with such tools is that if there are continual changes to the system being tested, the ‘recordings’ may have to be changed so much that it becomes very time-consuming to continuously update the scripts. Additionally, interpretation of results (screens, data, logs, etc.) can be a difficult task. Note that there are record/playback tools for text-based interfaces also, and for all types of platforms.
 Other automated tools can include:
code analyzers – monitor code complexity, adherence to
standards, etc.

coverage analyzers – these tools check which parts of the
code have been exercised by a test, and may
be oriented to code statement coverage,
condition coverage, path coverage, etc.

memory analyzers – such as bounds-checkers and leak detectors.

load/performance test tools – for testing client/server
and web applications under various load

web test tools – to check that links are valid, HTML code
usage is correct, client-side and
server-side programs work, a web site’s
interactions are secure.

other tools – for test case management, documentation
management, bug reporting, and configuration

24. What makes a good test engineer?

A good test engineer has a ‘test to break’ attitude, an ability to take the point of view of the customer, a strong desire for quality, and an attention to detail. Tact and diplomacy are useful in maintaining a cooperative relationship with developers, and an ability to communicate with both technical (developers) and non-technical (customers, management) people is useful. Previous software development experience can be helpful as it provides a deeper understanding of the software development process, gives the tester an appreciation for the developers’ point of view, and reduce the learning curve in automated test tool programming. Judgment skills are needed to assess high-risk areas of an application on which to focus testing efforts when time is limited.

25. What makes a good Software QA engineer?

The same qualities a good tester has are useful for a QA engineer. Additionally, they must be able to understand the entire software development process and how it can fit into the business approach and goals of the organization. Communication skills and the ability to understand various sides of issues are important. In organizations in the early stages of implementing QA processes, patience and diplomacy are especially needed. An ability to find problems as well as to see ‘what’s missing’ is important for inspections and reviews.

26. What makes a good QA or Test manager?
A good QA, test, or QA/Test(combined) manager should:
 be familiar with the software development process
 be able to maintain enthusiasm of their team and promote a positive atmosphere, despite what is a somewhat ‘negative’ process (e.g., looking for or preventing problems)
 be able to promote teamwork to increase productivity
 be able to promote cooperation between software, test, and QA engineers
 have the diplomatic skills needed to promote improvements in QA processes
 have the ability to withstand pressures and say ‘no’ to other managers when quality is insufficient or QA processes are not being adhered to
 have people judgement skills for hiring and keeping skilled personnel
 be able to communicate with technical and non-technical people, engineers, managers, and customers.
 be able to run meetings and keep them focused

27. What’s the role of documentation in QA?
Critical. (Note that documentation can be electronic, not necessarily paper.) QA practices should be documented such that they are repeatable. Specifications, designs, business rules, inspection reports, configurations, code changes, test plans, test cases, bug reports, user manuals, etc. should all be documented. There should ideally be a system for easily finding and obtaining documents and determining what documentation will have a particular piece of information. Change management for documentation should be used if possible.

28. What’s the big deal about ‘requirements’?
One of the most reliable methods of insuring problems, or failure, in a complex software project is to have poorly documented requirements specifications. Requirements are the details describing an application’s externally-perceived functionality and properties. Requirements should be clear, complete, reasonably detailed, cohesive, attainable, and testable. A non-testable requirement would be, for example, ‘user-friendly’ (too subjective). A testable requirement would be something like ‘the user must enter their previously-assigned password to access the application’. Determining and organizing requirements details in a useful and efficient way can be a difficult effort; different methods are available depending on the particular project. Many books are available that describe various approaches to this task.
Care should be taken to involve ALL of a project’s significant ‘customers’ in the requirements process. ‘Customers’ could be in-house personnel or out, and could include end-users, customer acceptance testers, customer contract officers, customer management, future software maintenance engineers, salespeople, etc. Anyone who could later derail the project if their expectations aren’t met should be included if possible.
Organizations vary considerably in their handling of requirements specifications. Ideally, the requirements are spelled out in a document with statements such as ‘The product shall…..’. ‘Design’ specifications should not be confused with ‘requirements’; design specifications should be traceable back to the requirements.
In some organizations requirements may end up in high level project plans, functional specification documents, in design documents, or in other documents at various levels of detail. No matter what they are called, some type of documentation with detailed requirements will be needed by testers in order to properly plan and execute tests. Without such documentation, there will be no clear-cut way to determine if a software application is performing correctly.

29. What steps are needed to develop and run software tests?
The following are some of the steps to consider:
 Obtain requirements, functional design, and internal design specifications and other necessary documents
 Obtain budget and schedule requirements
 Determine project-related personnel and their responsibilities, reporting requirements, required standards and processes (such as release processes, change processes, etc.)
 Identify application’s higher-risk aspects, set priorities, and determine scope and limitations of tests
 Determine test approaches and methods – unit, integration, functional, system, load, usability tests, etc.
 Determine test environment requirements (hardware, software, communications, etc.)
 Determine testware requirements (record/playback tools, coverage analyzers, test tracking, problem/bug tracking, etc.)
 Determine test input data requirements
 Identify tasks, those responsible for tasks, and labor requirements
 Set schedule estimates, timelines, milestones
 Determine input equivalence classes, boundary value analyses, error classes
 Prepare test plan document and have needed reviews/approvals
 Write test cases
 Have needed reviews/inspections/approvals of test cases
 Prepare test environment and testware, obtain needed user manuals/reference documents/configuration guides/installation guides, set up test tracking processes, set up logging and archiving processes, set up or obtain test input data
 Obtain and install software releases
 Perform tests
 Evaluate and report results
 Track problems/bugs and fixes
 Retest as needed
 Maintain and update test plans, test cases, test environment, and testware through life cycle

30. What’s a ‘test plan’?

A software project test plan is a document that describes the objectives, scope, approach, and focus of a software testing effort. The process of preparing a test plan is a useful way to think through the efforts needed to validate the acceptability of a software product. The completed document will help people outside the test group understand the ‘why’ and ‘how’ of product validation. It should be thorough enough to be useful but not so thorough that no one outside the test group will read it. The following are some of the items that might be included in a test plan, depending on the particular project:
 Title
 Identification of software including version/release numbers
 Revision history of document including authors, dates, approvals
 Table of Contents
 Purpose of document, intended audience
 Objective of testing effort
 Software product overview
 Relevant related document list, such as requirements, design documents, other test plans, etc.
 Relevant standards or legal requirements
 Traceability requirements
 Relevant naming conventions and identifier conventions
 Overall software project organization and personnel/contact-info/responsibilties
 Test organization and personnel/contact-info/responsibilities
 Assumptions and dependencies
 Project risk analysis
 Testing priorities and focus
 Scope and limitations of testing
 Test outline – a decomposition of the test approach by test type, feature, functionality, process, system, module, etc. as applicable
 Outline of data input equivalence classes, boundary value analysis, error classes
 Test environment – hardware, operating systems, other required software, data configurations, interfaces to other systems
 Test environment validity analysis – differences between the test and production systems and their impact on test validity.
 Test environment setup and configuration issues
 Software migration processes
 Software CM processes
 Test data setup requirements
 Database setup requirements
 Outline of system-logging/error-logging/other capabilities, and tools such as screen capture software, that will be used to help describe and report bugs
 Discussion of any specialized software or hardware tools that will be used by testers to help track the cause or source of bugs
 Test automation – justification and overview
 Test tools to be used, including versions, patches, etc.
 Test script/test code maintenance processes and version control
 Problem tracking and resolution – tools and processes
 Project test metrics to be used
 Reporting requirements and testing deliverables
 Software entrance and exit criteria
 Initial sanity testing period and criteria
 Test suspension and restart criteria
 Personnel allocation
 Personnel pre-training needs
 Test site/location
 Outside test organizations to be utilized and their purpose, responsibilities, deliverables, contact persons, and coordination issues
 Relevant proprietary, classified, security, and licensing issues.
 Open issues
 Appendix – glossary, acronyms, etc.

31. What’s a ‘test case’?
 A test case is a document that describes an input, action, or event and an expected response, to determine if a feature of an application is working correctly. A test case should contain particulars such as test case identifier, test case name, objective, test conditions/setup, input data requirements, steps, and expected results.
 Note that the process of developing test cases can help find problems in the requirements or design of an application, since it requires completely thinking through the operation of the application. For this reason, it’s useful to prepare test cases early in the development cycle if possible.

32. What should be done after a bug is found?
The bug needs to be communicated and assigned to developers that can fix it. After the problem is resolved, fixes should be re-tested, and determinations made regarding requirements for regression testing to check that fixes didn’t create problems elsewhere. If a problem-tracking system is in place, it should encapsulate these processes. A variety of commercial problem-tracking/management software tools are available. The following are items to consider in the tracking process:
 Complete information such that developers can understand the bug, get an idea of it’s severity, and reproduce it if necessary.
 Bug identifier (number, ID, etc.)
 Current bug status (e.g., ‘Released for Retest’, ‘New’, etc.)
 The application name or identifier and version
 The function, module, feature, object, screen, etc. where the bug occurred
 Environment specifics, system, platform, relevant hardware specifics
 Test case name/number/identifier
 One-line bug description
 Full bug description
 Description of steps needed to reproduce the bug if not covered by a test case or if the developer doesn’t have easy access to the test case/test script/test tool
 Names and/or descriptions of file/data/messages/etc. used in test
 File excerpts/error messages/log file excerpts/screen shots/test tool logs that would be helpful in finding the cause of the problem
 Severity estimate (a 5-level range such as 1-5 or ‘critical’-to-‘low’ is common)
 Was the bug reproducible?
 Tester name
 Test date
 Bug reporting date
 Name of developer/group/organization the problem is assigned to
 Description of problem cause
 Description of fix
 Code section/file/module/class/method that was fixed
 Date of fix
 Application version that contains the fix
 Tester responsible for retest
 Retest date
 Retest results
 Regression testing requirements
 Tester responsible for regression tests
 Regression testing results
A reporting or tracking process should enable notification of appropriate personnel at various stages. For instance, testers need to know when retesting is needed, developers need to know when bugs are found and how to get the needed information, and reporting/summary capabilities are needed for managers.

33. What is ‘configuration management’?

Configuration management covers the processes used to control, coordinate, and track: code, requirements, documentation, problems, change requests, designs, tools/compilers/libraries/patches, changes made to them, and who makes the changes.

34. What if the software is so buggy it can’t really be tested at all?

The best bet in this situation is for the testers to go through the process of reporting whatever bugs or blocking-type problems initially show up, with the focus being on critical bugs. Since this type of problem can severely affect schedules, and indicates deeper problems in the software development process (such as insufficient unit testing or insufficient integration testing, poor design, improper build or release procedures, etc.) managers should be notified, and provided with some documentation as evidence of the problem.

35. How can it be known when to stop testing?

This can be difficult to determine. Many modern software applications are so complex, and run in such an interdependent environment, that complete testing can never be done. Common factors in deciding when to stop are:
 Deadlines (release deadlines, testing deadlines, etc.)
 Test cases completed with certain percentage passed
 Test budget depleted
 Coverage of code/functionality/requirements reaches a specified point
 Bug rate falls below a certain level
 Beta or alpha testing period ends

36. What if there isn’t enough time for thorough testing?

Use risk analysis to determine where testing should be focused.
Since it’s rarely possible to test every possible aspect of an application, every possible combination of events, every dependency, or everything that could go wrong, risk analysis is appropriate to most software development projects. This requires judgement skills, common sense, and experience. (If warranted, formal methods are also available.) Considerations can include:
 Which functionality is most important to the project’s intended purpose?
 Which functionality is most visible to the user?
 Which functionality has the largest safety impact?
 Which functionality has the largest financial impact on users?
 Which aspects of the application are most important to the customer?
 Which aspects of the application can be tested early in the development cycle?
 Which parts of the code are most complex, and thus most subject to errors?
 Which parts of the application were developed in rush or panic mode?
 Which aspects of similar/related previous projects caused problems?
 Which aspects of similar/related previous projects had large maintenance expenses?
 Which parts of the requirements and design are unclear or poorly thought out?
 What do the developers think are the highest-risk aspects of the application?
 What kinds of problems would cause the worst publicity?
 What kinds of problems would cause the most customer service complaints?
 What kinds of tests could easily cover multiple functionalities?
 Which tests will have the best high-risk-coverage to time-required ratio?

37. What can be done if requirements are changing continuously?
A common problem and a major headache.
 Work with the project’s stakeholders early on to understand how requirements might change so that alternate test plans and strategies can be worked out in advance, if possible.
 It’s helpful if the application’s initial design allows for some adaptability so that later changes do not require redoing the application from scratch.
 If the code is well-commented and well-documented this makes changes easier for the developers.
 Use rapid prototyping whenever possible to help customers feel sure of their requirements and minimize changes.
 The project’s initial schedule should allow for some extra time commensurate with the possibility of changes.
 Try to move new requirements to a ‘Phase 2’ version of an application, while using the original requirements for the ‘Phase 1’ version.
 Negotiate to allow only easily-implemented new requirements into the project, while moving more difficult new requirements into future versions of the application.
 Be sure that customers and management understand the scheduling impacts, inherent risks, and costs of significant requirements changes. Then let management or the customers (not the developers or testers) decide if the changes are warranted – after all, that’s their job.
 Balance the effort put into setting up automated testing with the expected effort required to re-do them to deal with changes.
 Try to design some flexibility into automated test scripts.
 Focus initial automated testing on application aspects that are most likely to remain unchanged.
 Devote appropriate effort to risk analysis of changes to minimize regression testing needs.
 Design some flexibility into test cases (this is not easily done; the best bet might be to minimize the detail in the test cases, or set up only higher-level generic-type test plans)
 Focus less on detailed test plans and test cases and more on ad hoc testing (with an understanding of the added risk that this entails).

38. What if the project isn’t big enough to justify extensive testing?

Consider the impact of project errors, not the size of the project. However, if extensive testing is still not justified, risk analysis is again needed and the same considerations as described previously in ‘What if there isn’t enough time for thorough testing?’ apply. The tester might then do ad hoc testing, or write up a limited test plan based on the risk analysis.

39. What if the application has functionality that wasn’t in the requirements?

It may take serious effort to determine if an application has significant unexpected or hidden functionality, and it would indicate deeper problems in the software development process. If the functionality isn’t necessary to the purpose of the application, it should be removed, as it may have unknown impacts or dependencies that were not taken into account by the designer or the customer. If not removed, design information will be needed to determine added testing needs or regression testing needs. Management should be made aware of any significant added risks as a result of the unexpected functionality. If the functionality only effects areas such as minor improvements in the user interface, for example, it may not be a significant risk.

40. How can Software QA processes be implemented without stifling productivity?
By implementing QA processes slowly over time, using consensus to reach agreement on processes, and adjusting and experimenting as an organization grows and matures, productivity will be improved instead of stifled. Problem prevention will lessen the need for problem detection, panics and burn-out will decrease, and there will be improved focus and less wasted effort. At the same time, attempts should be made to keep processes simple and efficient, minimize paperwork, promote computer-based processes and automated tracking and reporting, minimize time required in meetings, and promote training as part of the QA process. However, no one – especially talented technical types – likes rules or bureacracy, and in the short run things may slow down a bit. A typical scenario would be that more days of planning and development will be needed, but less time will be required for late-night bug-fixing and calming of irate customers.

41. What if an organization is growing so fast that fixed QA processes are impossible?
This is a common problem in the software industry, especially in new technology areas. There is no easy solution in this situation, other than:
 Hire good people
 Management should ‘ruthlessly prioritize’ quality issues and maintain focus on the customer
 Everyone in the organization should be clear on what ‘quality’ means to the customer

42. How does a client/server environment affect testing?
Client/server applications can be quite complex due to the multiple dependencies among clients, data communications, hardware, and servers. Thus testing requirements can be extensive. When time is limited (as it usually is) the focus should be on integration and system testing. Additionally, load/stress/performance testing may be useful in determining client/server application limitations and capabilities. There are commercial tools to assist with such testing.

43. How can World Wide Web sites be tested?

Web sites are essentially client/server applications – with web servers and ‘browser’ clients. Consideration should be given to the interactions between html pages, TCP/IP communications, Internet connections, firewalls, applications that run in web pages (such as applets, javascript, plug-in applications), and applications that run on the server side (such as cgi scripts, database interfaces, logging applications, dynamic page generators, asp, etc.). Additionally, there are a wide variety of servers and browsers, various versions of each, small but sometimes significant differences between them, variations in connection speeds, rapidly changing technologies, and multiple standards and protocols. The end result is that testing for web sites can become a major ongoing effort. Other considerations might include:
 What are the expected loads on the server (e.g., number of hits per unit time?), and what kind of performance is required under such loads (such as web server response time, database query response times). What kinds of tools will be needed for performance testing (such as web load testing tools, other tools already in house that can be adapted, web robot downloading tools, etc.)?
 Who is the target audience? What kind of browsers will they be using? What kind of connection speeds will they by using? Are they intra- organization (thus with likely high connection speeds and similar browsers) or Internet-wide (thus with a wide variety of connection speeds and browser types)?
 What kind of performance is expected on the client side (e.g., how fast should pages appear, how fast should animations, applets, etc. load and run)?
 Will down time for server and content maintenance/upgrades be allowed? how much?
 What kinds of security (firewalls, encryptions, passwords, etc.) will be required and what is it expected to do? How can it be tested?
 How reliable are the site’s Internet connections required to be? And how does that affect backup system or redundant connection requirements and testing?
 What processes will be required to manage updates to the web site’s content, and what are the requirements for maintaining, tracking, and controlling page content, graphics, links, etc.?
 Which HTML specification will be adhered to? How strictly? What variations will be allowed for targeted browsers?
 Will there be any standards or requirements for page appearance and/or graphics throughout a site or parts of a site??
 How will internal and external links be validated and updated? how often?
 Can testing be done on the production system, or will a separate test system be required? How are browser caching, variations in browser option settings, dial-up connection variabilities, and real-world internet ‘traffic congestion’ problems to be accounted for in testing?
 How extensive or customized are the server logging and reporting requirements; are they considered an integral part of the system and do they require testing?
 How are cgi programs, applets, javascripts, ActiveX components, etc. to be maintained, tracked, controlled, and tested?
 Pages should be 3-5 screens max unless content is tightly focused on a single topic. If larger, provide internal links within the page.
 The page layouts and design elements should be consistent throughout a site, so that it’s clear to the user that they’re still within a site.
 Pages should be as browser-independent as possible, or pages should be provided or generated based on the browser-type.
 All pages should have links external to the page; there should be no dead-end pages.
 The page owner, revision date, and a link to a contact person or organization should be included on each page.

44. How is testing affected by object-oriented designs?
Well-engineered object-oriented design can make it easier to trace from code to internal design to functional design to requirements. While there will be little affect on black box testing (where an understanding of the internal design of the application is unnecessary), white-box testing can be oriented to the application’s objects. If the application was well-designed this can simplify test design.

45. What is Extreme Programming and what’s it got to do with testing?
Extreme Programming (XP) is a software development approach for small teams on risk-prone projects with unstable requirements. It was created by Kent Beck who described the approach in his book ‘Extreme Programming Explained’. Testing (‘extreme testing’) is a core aspect of Extreme Programming. Programmers are expected to write unit and functional test code first – before the application is developed. Test code is under source control along with the rest of the code. Customers are expected to be an integral part of the project team and to help develope scenarios for acceptance/black box testing. Acceptance tests are preferably automated, and are modified and rerun for each of the frequent development iterations. QA and test personnel are also required to be an integral part of the project team. Detailed requirements documentation is not used, and frequent re-scheduling, re-estimating, and re-prioritizing is expected.

46. Common Software Errors


This document takes you through whirl-wind tour of common software errors. This is an excellent aid for software testing. It helps you to identify errors systematically and increases the efficiency of software testing and improves testing productivity. For more information, please refer Testing Computer Software, Wiley Edition.

Type of Errors

• User Interface Errors

• Error Handling

• Boundary related errors

• Calculation errors

• Initial and Later states
• Control flow errors

• Errors in Handling or Interpreting Data

• Race Conditions

• Load Conditions

• Hardware

• Source, Version and ID Control

• Testing Errors

Let us go through details of each kind of error.


User Interface Errors



Sl No

Possible Error Conditions


Excessive Functionality


Inflated impression of functionality


Inadequacy for the task at hand


Missing function


Wrong function


Functionality must be created by user


Doesn’t do what the user expects



Missing Information
Sl No Possible Error Conditions
1 No on Screen instructions
2 Assuming printed documentation is already available.
3 Undocumented features
4 States that appear impossible to exit
5 No cursor
6 Failure to acknowledge input
7 Failure to show activity during long delays
8 Failure to advise when a change will take effect
9 Failure to check for the same document being opened twice
Wrong, misleading, confusing information
10 Simple factual errors
11 Spelling errors
12 Inaccurate simplifications
13 Invalid metaphors
14 Confusing feature names
15 More than one name for the same feature
16 Information overland
17 When are data saved
18 Wrong function
19 Functionality must be created by user
20 Poor external modularity
Help text and error messages
21 Inappropriate reading levels
22 Verbosity
23 Inappropriate emotional tone
24 Factual errors
25 Context errors
26 Failure to identify the source of error
27 Forbidding a resource without saying why
28 Reporting non-errors
29 Failure to highlight the part of the screen
30 Failure to clear highlighting
31 Wrong/partial string displayed
32 Message displayed for too long or not long enough
Display Layout
33 Poor aesthetics in screen layout
34 Menu Layout errors
35 Dialog box layout errors
36 Obscured Instructions
37 Misuse of flash
38 Misuse of color
39 Heavy reliance on color
40 Inconsistent with the style of the environment
41 Cannot get rid of on screen information
42 Can’t output certain data
43 Can’t redirect output
44 Format incompatible with a follow-up process
45 Must output too little or too much
46 Can’t control output layout
47 Absurd printout level of precision
48 Can’t control labeling of tables or figures
49 Can’t control scaling of graphs
50 Program Speed
51 User Throughput
52 Can’t redirect output
53 Perceived performance
54 Slow program
55 slow echoing
56 how to reduce user throughput
57 Poor responsiveness
58 No type ahead
59 No warning that the operation takes long time
60 No progress reports
61 Problems with time-outs
62 Program pesters you

ogram Rigidity

User tailorability
Sl No Possible Error Conditions
1 Can’t turn off case sensitivity
2 Can’t tailor to hardware at hand
3 Can’t change device initialization
4 Can’t turn off automatic changes
5 Can’t slow down/speed up scrolling
6 Can’t do what you did last time
7 Failure to execute a customization commands
8 Failure to save customization commands
9 Side effects of feature changes
10 Can’t turn off the noise
11 Infinite tailorability
Who is in control?
12 Unnecessary imposition of a conceptual style
13 Novice friendly, experienced hostile
14 Surplus or redundant information required
15 Unnecessary repetition of steps
16 Unnecessary limits

Command Structure and Rigidity

Sl No Possible Error Conditions
1 Optimizations
2 Inconsistent syntax
3 Inconsistent command entry style
4 Inconsistent abbreviations
5 Inconsistent termination rule
6 Inconsistent command options
7 Similarly named commands
8 Inconsistent Capitalization
9 Inconsistent menu position
10 Inconsistent function key usage
11 Inconsistent error handling rules
12 Inconsistent editing rules
13 Inconsistent data saving rules
Time Wasters
14 Garden paths
15 choice can’t be taken
16 Are you really, really sure
17 Obscurely or idiosyncratically named commands
18 Excessively complex menu hierarchy
19 Inadequate menu navigation options
20 Too many paths to the same place
21 You can’t get there from here
22 Related commands relegated to unrelated menus
23 Unrelated commands tossed under the same menu
Command Lines
24 Forced distinction between uppercase and lowercase
25 Reversed parameters
26 Full command names are not allowed
27 Abbreviations are not allowed
28 Demands complex input on one line
29 no batch input
30 can’t edit commands
Inappropriate use of key board
31 Failure to use cursor, edit, or function keys
32 Non std use of cursor and edit keys
33 non-standard use of function keys
34 Failure to filter invalid keys
35 Failure to indicate key board state changes

Missing Commands

State transitions
Sl No Possible Error Conditions
1 Can’t do nothing and leave
2 Can’t quit mid-program
3 Can’t stop mid-command
4 Can’t pause
Disaster prevention
5 No backup facility
6 No undo
7 No are you sure
8 No incremental saves
Disaster prevention
9 Inconsistent menu position
10 Inconsistent function key usage
11 Inconsistent error handling rules
12 Inconsistent editing rules
13 Inconsistent data saving rules
Error handling by the user
14 No user specifiable filters
15 Awkward error correction
16 Can’t include comments
17 Can’t display relationships between variables
18 Inadequate privacy or security
19 Obsession with security
20 Can’t hide menus
21 Doesn’t support standard OS features
22 Doesn’t allow long names

Error Handling

Error prevention

Sl No Possible Error Conditions
1 Inadequate initial state validation
2 Inadequate tests of user input
3 Inadequate protection against corrupted data
4 Inadequate tests of passed parameters
5 Inadequate protection against operating system bugs
6 Inadequate protection against malicious use
7 Inadequate version control

Error Detection

l No Possible Error Conditions
1 ignores overflow
2 ignores impossible values
3 ignores implausible values
4 ignores error flag
5 ignores hardware fault or error conditions
6 data comparison

Error Recovery

Sl No Possible Error Conditions
1 automatic error detection
2 failure to report error
3 failure to set an error flag
4 where does the program go back to
5 aborting errors
6 recovery from hardware problems
7 no escape from missing disks

Boundary related errors

Sl No Possible Error Conditions
1 Numeric boundaries
2 Equality as boundary
3 Boundaries on numerosity
4 Boundaries in space
5 Boundaries in time
6 Boundaries in loop
7 Boundaries in memory
8 Boundaries with data structure
9 Hardware related boundaries
10 Invisible boundaries
11 Mishandling of boundary case
12 Wrong boundary
13 Mishandling of cases outside boundary

Calculation Errors

Sl No Possible Error Conditions
1 Bad Logic
2 Bad Arithmetic
3 Imprecise Calculations
4 Outdated constants
5 Calculation errors
6 Impossible parenthesis
7 Wrong order of calculations
8 Bad underlying functions
9 Overflow and Underflow
10 Truncation and Round-off error
11 Confusion about the representation of data
12 Incorrect conversion from one data representation to another
13 Wrong Formula
14 Incorrect Approximation

Race Conditions

Sl No Possible Error Conditions
1 Races in updating data
2 Assumption that one event or task finished before another begins
3 Assumptions that one event or task has finished before another begins
4 Assumptions that input won’t occur during a brief processing interval
5 Assumptions that interrupts won’t occur during brief interval
6 Resource races
7 Assumptions that a person, device or process will respond quickly
8 Options out of sync during display changes
9 Tasks starts before its prerequisites are met
10 Messages cross or don’t arrive in the order sent

Initial and Later States

Sl No Possible Error Conditions
1 Failure to set data item to zero
2 Failure to initialize a loop-control variable
3 Failure to initialize a or re-initialize a pointer
4 Failure to clear a string
5 Failure to initialize a register
6 Failure to clear a flag
7 Data were supposed to be initialized elsewhere
8 Failure to re-initialize
9 Assumption that data were not re-initialized
10 Confusion between static and dynamic storage
11 Data modifications by side effect
12 Incorrect initialization

Control Flow Errors

Program runs amok

Sl No Possible Error Conditions
1 Jumping to a routine that isn’t resident
2 Re-entrance
3 Variables contains embedded command names
4 Wrong returning state assumed
5 Exception handling based exits

Return to wrong place

Sl No Possible Error Conditions
1 Corrupted Stack
2 Stack underflow/overflow
3 GOTO rather than RETURN from sub-routine


Sl No Possible Error Conditions
1 Wrong interrupt vector
2 Failure to restore or update interrupt vector
3 Invalid restart after an interrupt
4 Failure to block or un-block interrupts

Program Stops

Sl No Possible Error Conditions
1 Dead crash
2 Syntax error reported at run time
3 Waiting for impossible condition or combinations of conditions
4 Wrong user or process priority

Error Detection

Sl No Possible Error Conditions
1 infinite loop
2 Wrong starting value for the loop control variables
3 Accidental change of loop control variables
4 Command that do or don’t belong inside the loop
5 Command that do or don’t belong inside the loop
6 Improper loop nesting

If Then Else , Or may not

Sl No Possible Error Conditions
1 Wrong inequalities
2 Comparison sometimes yields wrong result
3 Not equal verses equal when there are three cases
4 Testing floating point values for equality
5 confusion between inclusive and exclusive OR
6 Incorrectly negating a logical expression
7 Assignment equal instead of test equal
8 Commands being inside the THEN or ELSE clause
9 Commands that don’t belong either case
10 Failure to test a flag
11 Failure to clear a flag

Multiple Cases

Sl No Possible Error Conditions
1 Missing default
2 Wrong default
3 Missing cases
4 Overlapping cases
5 Invalid or impossible cases
6 Commands being inside the THEN or ELSE clause
7 Case should be sub-divided

Errors Handling or Interpreting Data

Problems in passing data between routines

Sl No Possible Error Conditions
1 Parameter list variables out of order or missing
2 Data Type errors
3 Aliases and shifting interpretations of the same area of memory
4 Misunderstood data values
5 inadequate error information
6 Failure to clean up data on exception handling
7 Outdated copies of data
8 Related variable get out of synch
9 Local setting of global data
10 Global use of local variables
11 Wrong mask in bit fields
12 Wrong value from table

Data boundaries

Sl No Possible Error Conditions
1 Un-terminated null strings
2 Early end of string
3 Read/Write past end of data structure or an element in it

Read outside the limits of message buffer

Sl No Possible Error Conditions
1 Complier padding to word boundaries
2 value stack underflow/overflow
3 Trampling another process’s code or data

Messaging Problems

Sl No Possible Error Conditions
1 Messages sent to wrong process or port
2 Failure to validate an incoming message
3 Lost or out of synch messages
4 Message sent to only N of N+1 processes

Data Storage corruption

Sl No Possible Error Conditions
1 Overwritten changes
2 Data entry not saved
3 Too much data for receiving process to handle
4 Overwriting a file after an error exit or user abort

Load Conditions

Sl No Possible Error Conditions
1 Required resources are not available
2 No available large memory area
3 Input buffer or queue not deep enough
4 Doesn’t clear item from queue, buffer or stock
5 Lost Messages
6 Performance costs
7 Race condition windows expand
8 Doesn’t abbreviate under load
9 Doesn’t recognize that another process abbreviates output under load
10 Low priority tasks not put off
11 Low priority tasks never done

Doesn’t return a resource

Sl No Possible Error Conditions
1 Doesn’t indicate that it’s done with a device
2 Doesn’t erase old files from mass storage
3 Doesn’t return unused memory
4 Wastes computer time


Sl No Possible Error Conditions
1 Wrong Device
2 Wrong Device Address
3 Device unavailable
4 Device returned to wrong type of pool
5 Device use forbidden to caller
6 Specifies wrong privilege level for the device
7 Noisy Channel
8 Channel goes down
9 Time-out problems
10 Wrong storage device
11 Doesn’t check the directory of current disk
12 Doesn’t close the file
13 Unexpected end of file
14 Disk sector bug and other length dependent errors
15 Wrong operation or instruction codes
16 Misunderstood status or return code
17 Underutilizing device intelligence
18 Paging mechanism ignored or misunderstood
19 Ignores channel throughput limits
20 Assuming device is or isn’t or should be or shouldn’t be initialized
21 Assumes programmable function keys are programmed correctly

Source, Version, ID Control

Sl No Possible Error Conditions
1 Old bugs mysteriously re appear
2 Failure to update multiple copies of data or program files
3 No title
4 No version ID
5 Wrong version number of title screen
6 No copy right message or bad one
7 Archived source doesn’t compile into a match for shipping code
8 Manufactured disks don’t work or contain wrong code or data

Testing Errors

Missing bugs in the program

Sl No Possible Error Conditions
1 Failure to notice a problem
2 You don’t know what the correct test results are
3 You are bored or inattentive
4 Misreading the Screen
5 Failure to report problem
6 Failure to execute a planned test
7 Failure to use the most promising test case
8 Ignoring programmer’s suggestions

Finding bugs that aren’t in the program

Sl No Possible Error Conditions
1 Errors in testing programs
2 Corrupted data files
3 Misinterpreted specifications or documentation

Poor reporting

Sl No Possible Error Conditions
1 Illegible reports
2 Failure to make it clear how to reproduce the problem
3 Failure to say you can’t reproduce the problem
4 Failure to check your report
5 Failure to report timing dependencies
6 Failure to simplify conditions
7 Concentration on trivia
8 Abusive language


Poor Tracking and follow-up

Sl No

Possible Error Conditions


Failure to provide summary report


Failure to re-report serious bug


Failure to check for unresolved problems just before release


Failure to verify fixes

47. Designing Unit Test Cases

Executive Summary

Producing a test specification, including the design of test cases, is the level of test design which has the highest degree of creative input. Furthermore, unit test specifications will usually be produced by a large number of staff with a wide range of experience, not just a few experts.

This paper provides a general process for developing unit test specifications and then describes some specific design techniques for designing unit test cases. It serves as a tutorial for developers who are new to formal testing of software, and as a reminder of some finer points for experienced software testers.

A. Introduction

The design of tests is subject to the same basic engineering principles as the design of software. Good design consists of a number of stages which progressively elaborate the design. Good test design consists of a number of stages which progressively elaborate the design of tests:

 Test strategy;
 Test planning;
 Test specification;
 Test procedure.

These four stages of test design apply to all levels of testing, from unit testing through to system testing. This paper concentrates on the specification of unit tests; i.e. the design of individual unit test cases within unit test specifications. A more detailed description of the four stages of test design can be found in the IPL paper “An Introduction to Software Testing”.

The design of tests has to be driven by the specification of the software. For unit testing, tests are designed to verify that an individual unit implements all design decisions made in the unit’s design specification. A thorough unit test specification should include positive testing, that the unit does what it is supposed to do, and also negative testing, that the unit does not do anything that it is not supposed to do.

Producing a test specification, including the design of test cases, is the level of test design which has the highest degree of creative input. Furthermore, unit test specifications will usually be produced by a large number of staff with a wide range of experience, not just a few experts.

This paper provides a general process for developing unit test specifications, and then describes some specific design techniques for designing unit test cases. It serves as a tutorial for developers who are new to formal testing of software, and as a reminder of some finer points for experienced software testers.

B. Developing Unit Test Specifications

Once a unit has been designed, the next development step is to design the unit tests. An important point here is that it is more rigorous to design the tests before the code is written. If the code was written first, it would be too tempting to test the software against what it is observed to do (which is not really testing at all), rather than against what it is specified to do.

A unit test specification comprises a sequence of unit test cases. Each unit test case should include four essential elements:

 A statement of the initial state of the unit, the starting point of the test case (this is only applicable where a unit maintains state between calls);
 The inputs to the unit, including the value of any external data read by the unit;
 What the test case actually tests, in terms of the functionality of the unit and the analysis used in the design of the test case (for example, which decisions within the unit are tested);
 The expected outcome of the test case (the expected outcome of a test case should always be defined in the test specification, prior to test execution).

The following subsections of this paper provide a six step general process for developing a unit test specification as a set of individual unit test cases. For each step of the process, suitable test case design techniques are suggested. (Note that these are only suggestions. Individual circumstances may be better served by other test case design techniques). Section 3 of this paper then describes in detail a selection of techniques which can be used within this process to help design test cases.

B.1 Step 1 – Make it Run

The purpose of the first test case in any unit test specification should be to execute the unit under test in the simplest way possible. When the tests are actually executed, knowing that at least the first unit test will execute is a good confidence boost. If it will not execute, then it is preferable to have something as simple as possible as a starting point for debugging.

Suitable techniques:

– Specification derived tests
– Equivalence partitioning

B.2 Step 2 – Positive Testing

Test cases should be designed to show that the unit under test does what it is supposed to do. The test designer should walk through the relevant specifications; each test case should test one or more statements of specification. Where more than one specification is involved, it is best to make the sequence of test cases correspond to the sequence of statements in the primary specification for the unit.

Suitable techniques:

– Specification derived tests
– Equivalence partitioning
– State-transition testing

B.3. Step 3 – Negative Testing

Existing test cases should be enhanced and further test cases should be designed to show that the software does not do anything that it is not specified to do. This step depends primarily upon error guessing, relying upon the experience of the test designer to anticipate problem areas.

Suitable techniques:

– Error guessing
– Boundary value analysis
– Internal boundary value testing
– State-transition testing

B.4. Step 4 – Special Considerations

Where appropriate, test cases should be designed to address issues such as performance, safety requirements and security requirements. Particularly in the cases of safety and security, it can be convenient to give test cases special emphasis to facilitate security analysis or safety analysis and certification. Test cases already designed which address security issues or safety hazards should be identified in the unit test specification. Further test cases should then be added to the unit test specification to ensure that all security issues and safety hazards applicable to the unit will be fully addressed.

Suitable techniques:

– Specification derived tests

B.5. Step 5 – Coverage Tests

The test coverage likely to be achieved by the designed test cases should be visualised. Further test cases can then be added to the unit test specification to achieve specific test coverage objectives. Once coverage tests have been designed, the test procedure can be developed and the tests executed.

Suitable techniques:

– Branch testing
– Condition testing
– Data definition-use testing
– State-transition testing

B.6. Test Execution

A test specification designed using the above five steps should in most cases provide a thorough test for a unit. At this point the test specification can be used to develop an actual test procedure, and the test procedure used to execute the tests. For users of AdaTEST or Cantata, the test procedure will be an AdaTEST or Cantata test script.

Execution of the test procedure will identify errors in the unit which can be corrected and the unit re-tested. Dynamic analysis during execution of the test procedure will yield a measure of test coverage, indicating whether coverage objectives have been achieved. There is therefore a further coverage completion step in the process of designing test specifications.

B.7. Step 6 – Coverage Completion

Depending upon an organization’s standards for the specification of a unit, there may be no structural specification of processing within a unit other than the code itself. There are also likely to have been human errors made in the development of a test specification. Consequently, there may be complex decision conditions, loops and branches within the code for which coverage targets may not have been met when tests were executed. Where coverage objectives are not achieved, analysis must be conducted to determine why. Failure to achieve a coverage objective may be due to:

 Infeasible paths or conditions – the corrective action should be to annotate the test specification to provide a detailed justification of why the path or condition is not tested. AdaTEST provides some facilities to help exclude infeasible conditions from Boolean coverage metrics.
 Unreachable or redundant code – the corrective action will probably be to delete the offending code. It is easy to make mistakes in this analysis, particularly where defensive programming techniques have been used. If there is any doubt, defensive programming should not be deleted.
 Insufficient test cases – test cases should be refined and further test cases added to a test specification to fill the gaps in test coverage.

Ideally, the coverage completion step should be conducted without looking at the actual code. However, in practice some sight of the code may be necessary in order to achieve coverage targets. It is vital that all test designers should recognize that use of the coverage completion step should be minimized. The most effective testing will come from analysis and specification, not from experimentation and over dependence upon the coverage completion step to cover for sloppy test design.

Suitable techniques:

– Branch testing
– Condition testing
– Data definition-use testing
– State-transition testing

B.8. General Guidance

Note that the first five steps in producing a test specification can be achieved:

 Solely from design documentation;
 Without looking at the actual code;
 Prior to developing the actual test procedure.

It is usually a good idea to avoid long sequences of test cases which depend upon the outcome of preceding test cases. An error identified by a test case early in the sequence could cause secondary errors and reduce the amount of real testing achieved when the tests are executed.

The process of designing test cases, including executing them as “thought experiments”, often identifies bugs before the software has even been built. It is not uncommon to find more bugs when designing tests than when executing tests.

Throughout unit test design, the primary input should be the specification documents for the unit under test. While use of actual code as an input to the test design process may be necessary in some circumstances, test designers must take care that they are not testing the code against itself. A test specification developed from the code will only prove that the code does what the code does, not that it does what it is supposed to do.

2.1 Introduction

The purpose of this dissertation is to increase understanding of how experienced practitioners as individuals evaluate diagrammatic models in Formal Technical Review (FTR). In this research, those aspects of FTR relating to evaluation of an artifact by practitioners as individuals are referred to as Practitioner Evaluation (PE). The relevant FTR literature is reviewed for theory and research applicable to PE. However, FTR developed pragmatically without relation to underlying cognitive theory, and the literature consists primarily of case studies with a very limited number of controlled experiments.

Other work on the evaluation of diagrams and graphs is also reviewed for possible theoretical models that could be used in the current research. Human-Computer Interaction (HCI) is an Information Systems area that has drawn extensively on cognitive science to develop and evaluate Graphical User Interfaces (GUIs). A brief overview of cognitive-based approaches utilized in HCI is presented. One of these approaches, the Human Information Processing System model, in which the human mind is treated as an information-processing system, provides the cognitive theoretical model for this research and is discussed separately because of its importance. Work on attention and the comprehension of graphics is also briefly reviewed.

Two further areas are identified as necessary for the development of the research task and tools: (1) types of diagrammatic models and (2) types of software defects. Relevant work in each of these areas is briefly reviewed and, since typologies appropriate to this research were not located, appropriate typologies are developed.

2.2 Formal Technical Review

Software review as a technique to detect software defects is not new — it has been used since the earliest days of programming. For example, Babbage and von Neumann regularly asked colleagues to examine their programs [Freedman and Weinberg 1990], and in the 1950s and 1960s, large software projects often included some type of software review [Knight and Myers 1993]. However, the first significant formalization of software review practice is generally considered to be the development by Michael Fagan [1976] of a species of FTR that he called “inspection.”

Following Tjahjono [1996, 2], Formal Technical Review may be defined as any “evaluation technique that involves the bringing together of a group of technical [and sometimes non-technical] personnel to analyze a software artifact, typically with the goal of discovering errors or other anomalies.” As such, FTR has the following distinguishing characteristics:

1. Formal process.
2. Use of groups or teams. Most FTR techniques involve real groups, but nominal groups are used as well.
3. Review by knowledgeable individuals or practitioners.
4. Focus on detection of defects.

2.2.1 Types of Formal Technical Review

While the focus of this research is on the individual evaluation aspects of reviews, for context several other FTR techniques are discussed as well. Among the most common forms of FTR are the following:

1.Desk Checking, or reading over a program by hand while sitting at one’s desk, is the oldest software review technique [Adrion et al. 1982]. Strictly speaking, desk checking is not a form of FTR since it does not involve a formal process or a group. Moreover, desk checking is generally perceived as ineffective and unproductive due to (a) its lack of discipline and (b) the general ineffectiveness of people in detecting their own errors. To correct for the second problem, programmers often swap programs and check each other’s work. Since desk checking is an individual process not involving group dynamics, research in this area would be relevant but none applicable to the current research was found.
It should be noted that Humphrey [1995] has developed a review method, called Personal Review (PR), which is similar to desk checking. In PR, each programmer examines his own products to find as many defects as possible utilizing a disciplined process in conjunction with Humphrey’s Personal Software Process (PSP) to improve his own work. The review strategy includes the use of checklists to guide the review process, review metrics to improve the process, and defect causal analysis to prevent the same defects from recurring in the future. The approach taken in developing the Personal Review process is an engineering one; no reference is made in Humphrey [1995] to cognitive theory.
2. Peer Rating is a technique in which anonymous programs are evaluated in terms of their overall quality, maintainability, extensibility, usability and clarity by selected programmers who have similar backgrounds [Myers 1979]. Shneiderman [1980] suggests that peer ratings of programs are productive, enjoyable, and non-threatening experiences. The technique is often referred to as Peer Reviews [Shneiderman 1980], but some authors use the term peer reviews for generic review methods involving peers [Paulk et al 1993; Humphrey 1989].

3. Walkthroughs are presentation reviews in which a review participant, usually the software author, narrates a description of the software and the other members of the review group provide feedback throughout the presentation [Freedman and Weinberg 1990; Gilb and Graham 1993]. It should be noted that the term “walkthrough” has been used in the literature variously. Some authors unite it with “structured” and treat it as a disciplined, formal review process [Myers 1979; Yourdon 1989; Adrion et al. 1982]. However, the literature generally describes walkthrough as an undisciplined process without advance preparation on the part of reviewers and with the meeting focus on education of participants [Fagan 1976].

4. Round-robin Review is a evaluation process in which a copy of the review materials is made available and routed to each participant; the reviewers then write their comments/questions concerning the materials and pass the materials with comments to another reviewer and to the moderator or author eventually [Hart 1982].

5. Inspection was developed by Fagan [1976, 1986] as a well-planned and well-defined group review process to detect software defects – defect repair occurs outside the scope of the process. The original Fagan Inspection (FI) is the most cited review method in the literature and is the source for a variety of similar inspection techniques [Tjahjono 1996]. Among the FI-derived techniques are Active Design Review [Parnas and Weiss 1987], Phased Inspection [Knight and Myers 1993], N-Fold Inspection [Schneider et al. 1992], and FTArm [Tjahjono 1996]. Unlike the review techniques previously discussed, inspection is often used to control the quality and productivity of the development process.

A Fagan Inspection consists of six well-defined phases:

i. Planning. Participants are selected and the materials to be reviewed are prepared and checked for review suitability.
ii. Overview. The author educates the participants about the review materials through a presentation.
iii. Preparation. The participants learn the materials individually.
iv. Meeting. The reader (a participant other than the author) narrates or paraphrases the review materials statement by statement, and the other participants raise issues and questions. Questions continue on a point only until an error is recognized or the item is deemed correct.
v. Rework. The author fixes the defects identified in the meeting.
vi. Follow-up. The “corrected” products are reinspected.

Practitioner Evaluation is primarily associated with the Preparation phase.

In addition to classification by technique-type, FTR may also be classified on other dimensions, including the following:

A. Small vs. Large Team Reviews. Siy [1996] classifies reviews into those conducted by small (1-4 reviewers) [Bisant and Lyle 1996] and large (more than 4 reviewers) [Fagan 1976, 1986] teams. If each reviewer depends on different expertise and experiences, a large team should allow a wider variety of defects to be detected and thus better coverage. However, a large team requires more effort due to more individuals inspecting the artifact, generally involves greater scheduling problems [Ballman and Votta 1994], and may make it more difficult for all participants to participate fully.

B. No vs. Single vs. Multiple Session Reviews. The traditional Fagan Inspection provided for one session to inspect the software artifact, with the possibility of a follow-up session to inspect corrections. However, variants have been suggested.

Humphrey [1989] comments that three-quarters of the errors found in well-run inspections are found during preparation. Based on an economic analysis of a series of inspections at AT&T, Votta [1993] argues that inspection meetings are generally not economic and should be replaced with depositions, where the author and (optionally) the moderator meet separately with inspectors to collect their results.

On the other hand, some authors [Knight and Myers 1993; Schneider et al. 1992] have argued for multiple sessions, conducted either in series or parallel. Gilb and Graham [1993] do not use multiple inspection sessions but add a root cause analysis session immediately after the inspection meeting.

C. Nonsystematic vs. Systematic Defect-Detection Technique Reviews. The most frequently used detection methods (ad hoc and checklist) rely on nonsystematic techniques, and reviewer responsibilities are general and not differentiated for single session reviews [Siy 1996]. However, some methods employ more prescriptive techniques, such as questionnaires [Parnas and Weiss 1987] and correctness proofs [Britcher 1988].
D.Single Site vs. Multiple Site Reviews. The traditional FTR techniques have assumed that the group-meeting component would occur face-to-face at a single site. However, with improved telecommunications, and especially with computer support (see item F below), it has become increasingly feasible to conduct even the group meeting from multiple sites.
E. Synchronous vs. Asynchronous Reviews. The traditional FTR techniques have also assumed that the group meeting component would occur in real-time; i.e., synchronously. However, some newer techniques that eliminate the group meeting or are based on computer support utilize asynchronous reviews.

F. Manual vs. Computer-supported Reviews. In recent years, several computer supported review systems have been developed [Brothers et al. 1990; Johnson and Tjahjono 1993; Gintell et al. 1993; Mashayekhi et al 1994]. The type of support varies from simple augmentation of the manual practices [Brothers et al. 1990; Gintell et al. 1993] to totally new review methods [Johnson and Tjahjono 1993].

  1. anilkumar
    February 25, 2008 at 1:29 pm

    it’s good i want answer for the this question
    what is diff between static and dynamic testing?

  2. Maha
    February 27, 2008 at 5:23 pm

    It’s really a good and useful article and learnt a lot about QA.

  3. sandhya
    March 4, 2008 at 11:38 am

    process of finding bugs without executinig the codes is the static testing.findings bugs by executing the software is the dynamic testing.cost of defect will be less in static testing

  4. Kanthasamy
    March 4, 2008 at 2:04 pm

    its good…

  5. H.O
    March 8, 2008 at 10:24 pm

    Please,help me to have a better understanding of the activities below,
    Coordinating user acceptance testing;
    Coordinating systems releases and implementations

  6. Senthilkumar.G
    March 14, 2008 at 11:17 am

    What is Static Testing?
    Static testing is a form of software testing where the software isn’t actually used. This is in contrast to Dynamic testing. It is generally not detailed testing, but checks mainly for the sanity of the code, algorithm, or document. It is primarily syntax checking of the code or and manually reading of the code or document to find errors. This type of testing can be used by the developer who wrote the code, in isolation. Code reviews, inspections and walkthroughs are also used.Static testing is like this QA activities.
    What is Dynamic Testing?
    Dynamic Testing involves working with the software, giving input values and checking if the output is as expected. These are the Validation activities. Unit Tests, Integration Tests, System Tests and Acceptance Tests are few of the Dynamic Testing methodologies.

    • JOPTHI
      June 17, 2012 at 8:13 pm


  7. MKM
    April 3, 2008 at 5:23 am

    Please include information about the Software Testing certifications paths available

  8. shantha
    April 17, 2008 at 5:12 am

    This is shantha.Ur doing the great job here.
    1.What is walk through.


  9. Anonymous
    April 25, 2008 at 10:27 am

    For Static and Dynamic Testing do watch

  10. bharathi
    June 7, 2008 at 1:30 pm

    Hi Thaygu…

    Really its great thing what u have done, all r very useful informations,
    can u sent me the web testing process while we testing the web applications, b’coz i was finished with my 3 projects in windows appln, dont hv an idea abt web testing, can you sent me the process & basic intervw qust abt web testing????


  11. Abhijit
    June 17, 2008 at 5:59 am

    Hi Thaygu…
    This is Abhijit.
    It’s very much useful yaar !!!

  12. babu
    July 9, 2008 at 4:26 pm

    It’s very useful for me…
    what is the meaning of testbed?
    who prepared srs and brd?
    what is ajail testing?


  13. babu
    July 9, 2008 at 4:26 pm

    It’s very useful for me…
    what is the meaning of testbed?
    who prepared srs and brd?
    what is ajail testing?
    what is spiral testing?


  14. Deepti
    August 2, 2008 at 3:19 pm

    hi thiyagaranjan
    Thanks a lot……
    it really very helpful site for Testing guys…
    We can say that it is a complete Testing Site….

  15. sander
    August 13, 2008 at 2:15 am

    HI all
    I am searching softeware testing job. i need some sample test case. could you any one send the sample test case to my email id.

    Email ID:

  16. sugar singh
    September 29, 2008 at 8:57 am

    It’s really very useful for all tester guys,
    Would you post about automation test framework ?


  17. scottc
    January 12, 2009 at 6:02 am


    You’ve built a good library of common testing terms and problems. Particularly like your Load/Stress testing definitions – very concise and useful.

    I would define a few points differently – partly I think this comes down to different people and organisations using a common term in their own way (which we all do to some extent!)

    Verification is checking two things are the same. Ie. does the product match the specification for “xyz”.

    Validation however is checking that the defined behaviour is correct, or trying to think of scenarios where it will fail.

    ie. checking if the developer has implemented the specification is verification. Checking that the specification meets the user’s needs is validation.

    QA, QC and testing:
    Again, I think different organisations use common terms in different ways. Quality “Assurance” and “Control” literally (and I find in practise in most organisations), are about producing the same thing repeatedly and consistently. In software, achieving consistency across repetitions comes down to process.

    Testing on the other hand is not about consistency and repetition, it is about performing new tests and attempting to find new product failures.

    Keep up the good work!

  18. Anandhan
    March 26, 2009 at 1:12 pm

    Really it is simple to understand and lot of content to satisfied

  19. John
    May 2, 2009 at 8:54 am

    Please do not copy questions and anwers from This site content is illegal. Please remove the content or you may have to face legal charges.

  20. June 9, 2009 at 6:01 pm

    Very nice article

  21. June 9, 2009 at 6:02 pm

    Thanks for giving a good article..

  22. Hari
    June 9, 2009 at 6:11 pm


  23. Aniruddha
    August 10, 2009 at 2:15 pm

    Hello Sir,

    Thank you very much for Software Testing Q and A help.



  24. sarmistha
    February 23, 2010 at 7:54 am

    hi thiyagaranjan
    Thanks a lot……
    it really very helpful site for Testing guys…


  25. sarmistha
    February 23, 2010 at 7:55 am

    hi thiyagaranjan
    Thanks a lot……
    it really very helpful site for Testing guys…

  26. Dillip
    March 11, 2010 at 5:04 pm

    Hi Thiyagaranjan,

    I am a Software Test Engineer having 3.6 years of Experience in Software Manual Testing. I am currently working in Bangalore and looking for a change in my job. When i have gone through the Q & A part, i have learned the unknown thing, gave me a immense satisfaction & hope that i can find a best job in town easily in the near future.

    Hats off to ur Blog!

    Keep updating this!

    Thanking You!!!

    P S Dillip

  27. Vijayalaxmi Patil
    April 23, 2010 at 11:40 am

    Its really a good knowledge sharing….many points are been covered in this article..
    THANKS 🙂

  28. Srini
    September 23, 2010 at 8:57 am

    Realy Superb!
    Very useful for candidate who is going for QA Interview.It covers all the questions which I faced in the interview so far.

  29. syamala
    April 30, 2011 at 9:51 am

    this is really really good.

    Between negative and positive testing which one is more important.

  30. April 30, 2012 at 9:02 pm

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  32. August 25, 2014 at 8:08 am

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  33. ask
    April 21, 2015 at 5:43 am

    Great article.

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