Software Testing, Software Management, Software Configuration, Design and Deployment!

Version 1.2, November 2002Copyright (C) 2000,2001,2002
Free Software Foundation, Inc. 51 Franklin St, Fifth Floor,
Boston, MA 02110-1301 USA Everyone is permitted to copy and
distribute verbatim copies of this license document, but changing
it is not allowed.

Software testing

From Wikipedia, the free encyclopedia

Software testing is the process used to measure the quality of developed computer software.

Software Testing Portal

Introduction

How Software Defects arise

The International Software Testing Qualifications Board says that software faults occur through the following process:

A human being can make an error (mistake), which produces a defect (fault, bug) in the code, in software or a system, or in a document. If a defect in code is executed, the system will fail to do what it should do (or do something it shouldn’t), causing a failure. Defects in software, systems or documents may result in failures, but not all defects do so.^[1]

A fault can also turn into a failure when the environment is changed. Examples of these changes in environment include the software being run on a new hardware platform, alterations in source data or interacting with different software.^[2]

Inability to find all faults

A problem with software testing is that testing all combinations of inputs and preconditions is not feasible when testing anything other than a simple product.^[3] This means that the number of defects in a software product can be very large and defects that occur infrequently are difficult to find in testing.

When Testing is Carried Out

A common practice of software testing is that it is performed by an independent group of testers after the functionality is developed but before it is shipped to the customer.^[4] This practice often results in the testing phase being used as project buffer to compensate for project delays, thereby compromising the time devoted to testing.^[5] Another practice is to start software testing at the same moment the project starts and it is a continuous process until the project finishes.^[6]

This is highly problematic in terms of controlling changes to software: if faults or failures are found part way into the project, the decision to correct the software needs to be taken on the basis of whether or not these defects will delay the remainder of the project.^{[citation needed]} If the software does need correction, this needs to be rigorously controlled using a version numbering system, and software testers need to be accurate in knowing that they are testing the correct version, and will need to re-test the part of the software wherein the defects were found. The correct start point needs to be identified for retesting. There are added risks in that new defects may be introduced as part of the corrections, and the original requirement can also change part way through, in which instance previous successful tests may no longer meet the requirement and will need to be re-specified and redone (part of regression testing). Clearly the possibilities for projects being delayed and running over budget are significant.

Another common practice is for test suites to be developed during technical support escalation procedures. Such tests are then maintained in regression testing suites to ensure that future updates to the software don't repeat any of the known mistakes.

Finding Faults Early in the Process

It is commonly believed that the earlier a defect is found the cheaper it is to fix it.^[7] This is reasonable based on the risk of any given defect contributing to or being confused with further defects later in the system or process. In particular, if a defect erroneously changes the state of the data on which the software is operating, that data is no longer reliable and therefore any testing after that point cannot be relied on even if there are no further actual software defects.

In counterpoint, some emerging software disciplines such as extreme programming and the agile software development movement, adhere to a "test-driven software development" model. In this process unit tests are written first, by the software engineers (often with pair programming in the extreme programming methodology). Of course these tests fail initially; as they are expected to. Then as code is written it passes incrementally larger portions of the test suites. The test suites are continuously updated as new failure conditions and corner cases are discovered, and they are integrated with any regression tests that are developed.

Unit tests are maintained along with the rest of the software source code and generally integrated into the build process (with inherently interactive tests being relegated to a partially manual build acceptance process).

The software, tools, samples of data input and output, and configurations are all referred to collectively as a test harness.

Measuring Software Testing

Usually, quality is constrained to such topics as correctness, completeness, security,^{[citation needed]} but can also include more technical requirements as described under the ISO standard ISO 9126, such as capability, reliability, efficiency, portability, maintainability, compatibility, and usability.^{[citation needed]}

Testing is a process of technical investigation, performed on behalf of stakeholders, that is intended to reveal quality-related information about the product with respect to the context in which it is intended to operate. This includes, but is not limited to, the process of executing a program or application with the intent of finding errors. Quality is not an absolute; it is value to some person. With that in mind, testing can never completely establish the correctness of arbitrary computer software; testing furnishes a criticism or comparison that compares the state and behaviour of the product against a specification. An important point is that software testing should be distinguished from the separate discipline of Software Quality Assurance (SQA), which encompasses all business process areas, not just testing.

Today, software has grown in complexity and size. The software product developed by a developer is according to the System Requirement Specification. Every software product has a target audience. For example, a video game software has its audience completely different from banking software. Therefore, when an organization invests large sums in making a software product, it must ensure that the software product must be acceptable to the end users or its target audience. This is where Software Testing comes into play. Software testing is not merely finding defects or bugs in the software, it is the completely dedicated discipline of evaluating the quality of the software.

There are many approaches to software testing, but effective testing of complex products is essentially a to connote the dynamic analysis of the product—putting the product through its paces. Sometimes one therefore refers to reviews, walkthroughs or inspections as static testing, whereas actually running the program with a given set of test cases in a given development stage is often referred to as dynamic testing, to emphasize the fact that formal review processes form part of the overall testing scope.

Code coverage

Main article: Code coverage

Code coverage measures aim to show the degree to which the source code of a program has been tested.^[9] It is inherently a white box testing activity because it looks at the code directly. This allows the software team to examine parts of a system that are rarely tested and ensures that the most important function points have been tested.^[10] Two common forms of code coverage are statement coverage, which reports on the number of lines executed, and path coverage, which reports on the branches executed to complete the test. They both return a coverage metric, measured as a percentage.

Software Testing Measurements

There are a number of common software measures, often called "metrics", which are used to measure the state of the software or the adequacy of the testing:

• Bugs found per Tester per unit time (Day/Week/Month)^{[citation needed]}
• Total bugs found in a release^{[citation needed]}
• Total bugs found in a module / feature^{[citation needed]}
• Bugs found / fixed per build^{[citation needed]}
• Number of customer reported Bug - As a measure of testing effectiveness^{[citation needed]}
• Bug trend over the period in a release (Bugs should converge towards zero as the project gets closer to release) (It is possible that there are more cosmetic bugs found closer to release - in which case the number of critical bugs found is used instead of total number of bugs found)^{[citation needed]}
• Number of test cases executed per person per unit time^{[citation needed]}
• % of test cases executed so far, total Pass, total fail^{[citation needed]}
• Test Coverage^{[citation needed]}

History

The separation of debugging from testing was initially introduced by Glenford J. Myers in 1979.^[11] Although his attention was on breakage testing it illustrated the desire of the software engineering community to separate fundamental development activities, such as debugging, from that of verification. Dr. Dave Gelperin and Dr. William C. Hetzel classified in 1988 the phases and goals in software testing in the following stages:^[12]

1. Until 1956 - Debugging oriented^[13]
2. 1957-1978 - Demonstration oriented^[14]
3. 1983-1987 - Destruction oriented^[15]
4. 1983-1987 - Evaluation oriented^[16]
5. 1988-onward- Prevention oriented^[17]

White box, black box, and grey box testing

White box and black box testing are terms used to describe the point of view that a test engineer takes when designing test cases.

Black box testing treats the software as a black-box without any understanding as to how the internals behave. It aims to test the functionality according to the requirements.^[18]Thus, the tester inputs data and only sees the output from the test object. This level of testing usually requires thorough test cases to be provided to the tester who then can simply verify that for a given input, the output value (or behaviour), is the same as the expected value specified in the test case.

White box testing, however, is when the tester has access to the internal data structures, code, and algorithms. For this reason, unit testing and debugging can be classified as white-box testing and it usually requires writing code, or at a minimum, stepping through it, and thus requires more knowledge of the product than the black-box tester.^[19] If the software in test is an interface or API of any sort, white-box testing is almost always required.^{[citation needed]}

In recent years the term grey box testing has come into common usage. This involves having access to internal data structures and algorithms for purposes of designing the test cases, but testing at the user, or black-box level. Manipulating input data and formatting output do not qualify as grey-box because the input and output are clearly outside of the black-box we are calling the software under test. This is particularly important when conducting integration testing between two modules of code written by two different developers, where only the interfaces are exposed for test.

Grey box testing could be used in the context of testing a client-server environment when the tester has control over the input, inspects the value in a SQL database, and the output value, and then compares all three (the input, sql value, and output), to determine if the data got corrupt on the database insertion or retrieval.

Verification and validation

Main article: Verification and Validation (software)

Software testing is used in association with verification and validation (V&V). Verification is the checking of or testing of items, including software, for conformance and consistency with an associated specification. Software testing is just one kind of verification, which also uses techniques such as reviews, inspections, and walkthroughs. Validation is the process of checking what has been specified is what the user actually wanted.

• Verification: Have we built the software right (i.e., does it match the specification)?
• Validation: Have we built the right software (i.e., is this what the customer wants)?

Pre Release

• Unit testing tests the minimal software component, or module. Each unit (basic component) of the software is tested to verify that the detailed design for the unit has been correctly implemented. In an Object-oriented environment, this is usually at the class level, and the minimal unit tests include the constructors and destructors.^[20]
• Integration testing exposes defects in the interfaces and interaction between integrated components (modules). Progressively larger groups of tested software components corresponding to elements of the architectural design are integrated and tested until the software works as a system.
• Functional testing tests at any level (class, module, interface, or system) for proper functionality as defined in the specification. The use of a traceability matrix often helps with functional testing.
• System testing tests a completely integrated system to verify that it meets its requirements.
• System integration testing verifies that a system is integrated to any external or third party systems defined in the system requirements.
• Performance Testing validates whether the quality of service (sometimes called Non-functional requirements) parameters defined at the requirements stage is met by the final product.
• Acceptance testing can be conducted by the end-user, customer, or client to validate whether or not to accept the product. Acceptance testing may be performed as part of the hand-off process between any two phases of development. See also software release life cycle

Post Release

• Alpha testing is simulated or actual operational testing by potential users/customers or an independent test team at the developers' site. Alpha testing is often employed for off-the-shelf software as a form of internal acceptance testing, before the software goes to beta testing.
• Beta testing comes after alpha testing. Versions of the software, known as beta versions, are released to a limited audience outside of the company. The software is released to groups of people so that further testing can ensure the product has few faults or bugs. Sometimes, beta versions are made available to the open public to increase the feedback field to a maximal number of future users.

It should be noted that although both Alpha and Beta are referred to as testing it is in fact use immersion. The rigors that are applied are often unsystematic and many of the basic tenets of testing process are not used. The Alpha and Beta period provides insight into environmental and utilization conditions that can impact the software.

Regression Testing

Main article: Regression testing

After modifying software, either for a change in functionality or to fix defects, a regression test re-runs previously passing tests on the modified software to ensure that the modifications haven't unintentionally caused a regression of previous functionality.

Regression testing can be performed at any or all of the above test levels. These regression tests are often automated.

More specific forms of regression testing are known as Sanity testing, when quickly checking for bizarre behaviour, and Smoke testing when testing for basic functionality.

Test cases, suites, scripts, and scenarios

A test case is a software testing document, which consists of event, action, input, output, expected result, and actual result. Clinically defined a test case is an input and an expected result.^[21] This can be as pragmatic as 'for condition x your derived result is y', whereas other test cases described in more detail the input scenario and what results might be expected. It can occasionally be a series of steps (but often steps are contained in a separate test procedure that can be exercised against multiple test cases, as a matter of economy) but with one expected result or expected outcome. The optional fields are a test case ID, test step or order of execution number, related requirement(s), depth, test category, author, and check boxes for whether the test is automatable and has been automated. Larger test cases may also contain prerequisite states or steps, and descriptions. A test case should also contain a place for the actual result. These steps can be stored in a word processor document, spreadsheet, database, or other common repository. In a database system, you may also be able to see past test results and who generated the results and the system configuration used to generate those results. These past results would usually be stored in a separate table.

The term test script is the combination of a test case, test procedure, and test data. Initially the term was derived from the product of work created by automated regression test tools. Today, test scripts can be manual, automated, or a combination of both.

The most common term for a collection of test cases is a test suite. The test suite often also contains more detailed instructions or goals for each collection of test cases. It definitely contains a section where the tester identifies the system configuration used during testing. A group of test cases may also contain prerequisite states or steps, and descriptions of the following tests.

Collections of test cases are sometimes incorrectly termed a test plan. They might correctly be called a test specification. If sequence is specified, it can be called a test script, scenario, or procedure.

A sample testing cycle

Although testing varies between organizations, there is a cycle to testing:

1. Requirements Analysis: Testing should begin in the requirements phase of the software development life cycle.

   During the design phase, testers work with developers in determining what aspects of a design are testable and with what parameters those tests work.

2. Test Planning: Test Strategy, Test Plan(s), Test Bed creation.

   A lot of activities will be carried out during testing, so that a plan is needed.

3. Test Development: Test Procedures, Test Scenarios, Test Cases, Test Scripts to use in testing software.
4. Test Execution: Testers execute the software based on the plans and tests and report any errors found to the development team.
5. Test Reporting: Once testing is completed, testers generate metrics and make final reports on their test effort and whether or not the software tested is ready for release.
6. Retesting the Defects

Not all errors or defects reported must be fixed by a software development team. Some may be caused by errors in configuring the test software to match the development or production environment. Some defects can be handled by a workaround in the production environment. Others might be deferred to future releases of the software, or the deficiency might be accepted by the business user. There are yet other defects that may be rejected by the development team (of course, with due reason) if they deem it.

Controversy

Main article: Software testing controversies

Some of the major controversies include:

• What constitutes responsible software testing? - Members of the "context-driven" school of testing^[22] believe that there are no "best practices" of testing, but rather that testing is a set of skills that allow the tester to select or invent testing practices to suit each unique situation. Some contend that this belief directly contradicts standards such as the IEEE 829 test documentation standard, and organizations such as the Food and Drug Administration who promote them.^{[citation needed]}

• Agile vs. traditional - Should testers learn to work under conditions of uncertainty and constant change or should they aim at process "maturity"? The agile testing movement has popularity mainly in commercial circles,^{[citation needed]} whereas the CMM was embraced by government and military software providers.^{[citation needed]}

• Exploratory vs. scripted^{[citation needed]} - Should tests be designed at the same time as they are executed or should they be designed beforehand?

• Manual vs. automated - Some writers believe that test automation is so expensive relative to its value that it should be used sparingly.^[23] Others, such as advocates of agile development, recommend automating 100% of all tests.

• Software design vs. software implementation^{[citation needed]} - Should testing be carried out only at the end or throughout the whole process?

• Who watches the watchmen? - The idea is that any form of observation is also an interaction, that the act of testing can also affect that which is being tested.^{[citation needed]}

Certification

Several certification programs exist to support the professional aspirations of software testers and quality assurance specialists. No certification currently offered actually requires the applicant to demonstrate the ability to test software. No certification is based on a widely accepted body of knowledge. This has led some to declare that the testing field is not ready for certification.^[24] Certification itself cannot measure an individual's productivity, their skill, or practical knowledge, and cannot guarantee their competence, or professionalism as a tester.^[25]

Certifications can be grouped into: exam-based and education-based. Exam-based certifications: For these there is the need to pass an exam, which can also be learned by self-study: e.g. for ISTQB or QAI. Education-based certifications are instructor-led sessions, where each course has to be passed, e.g. IIST (International Institute for Software Testing).

Testing certifications

• CSTE offered by the Quality Assurance Institute (QAI)^[26]
• CSTP offered by the International Institute for Software Testing^[27]
• CSTP (TM) (Australian Version) offered by the K. J. Ross & Associates^[28]
• CATe offered by the International Institute for Software Testing^[29]
• ISEB offered by the Information Systems Examinations Board
• ISTQB offered by the International Software Testing Qualification Board

Quality assurance certifications

• CSQE offered by the American Society for Quality (ASQ)^[30]
• CSQA offered by the Quality Assurance Institute (QAI)^[31]

Roles in software testing

Software testing can be done by software testers. Until the 1950s the term software tester was used generally, but later it was also seen as a separate profession. Regarding the periods and the different goals in software testing^[32] there have been established different roles: test lead/manager, tester, test designer, test automater/automation developer, and test administrator.

Relationship with Software Quality Assurance

Software testing may be viewed as an important part of the Software Quality Assurance (SQA) process.^{[citation needed]} In SQA, software process specialists and auditors take a broader view on software and its development. They examine and change the software engineering process itself to reduce the amount of faults that end up in defect rate. What constitutes an acceptable defect rate depends on the nature of the software. An arcade video game designed to simulate flying an airplane would presumably have a much higher tolerance for defects than software used to control an actual airliner. Although there are close links with SQA testing departments often exist independently, and there may be no SQA areas in some companies.

See also

Test Techniques

• All-pairs testing
• Characterization Test
• Dynamic program analysis
• Equivalence partitioning
• Fuzz testing
• Model-based testing
• Pseudolocalization
• Risk-based testing
• Reverse Semantic Traceability
• Static code analysis

Testing Tools

• Defect tracking
• Keyword-driven testing
• Session-based test
• Soak testing

Testing Terms

• Design predicates
• Development stage
• Elephant in Cairo
• Tester Driven Development
• Test vector
• Performance Engineering
• Formal verification

Specific Tests

• GUI software testing
• Search Based Software Engineering
• Security Testing
• Web testing

Quotes

• "An effective way to test code is to exercise it at its natural boundaries." -- Brian Kernighan
• "Program testing can be used to show the presence of bugs, but never to show their absence!" -- Edsger Dijkstra
• "Beware of bugs in the above code; I have only proved it correct, not tried it." -- Donald Knuth
• "A relatively small number of causes will typically produce a large majority of the problems or defects (80/20 Rule)." -- Pareto principle
• "given enough eyeballs, all bugs are shallow." -- Linus's Law according to Eric S. Raymond

References

External links

At Wikiversity you can learn more and teach others about Software testing at:

The Department of Software testing

• Software testing tools and products at the Open Directory Project
• Is Application Testing in Financial Services Making the Grade?
• Blogs on Software Quality & Testing
• AppLab's CEO Sashi Reddi sees potential of global software testing Development Market