Unit testing

In computer programming, unit testing is a software testing method by which individual units of source code, sets of one or more computer program modules together with associated control data, usage procedures, and operating procedures, are tested to determine whether they are fit for use.[1] Intuitively, one can view a unit as the smallest testable part of an application. In procedural programming, a unit could be an entire module, but it is more commonly an individual function or procedure. In object-oriented programming, a unit is often an entire interface, such as a class, but could be an individual method.[2] Unit tests are short code fragments[3] created by programmers or occasionally by white box testers during the development process. It forms the basis for component testing.[4]

Ideally, each test case is independent from the others. Substitutes such as method stubs, mock objects,[5] fakes, and test harnesses can be used to assist testing a module in isolation. Unit tests are typically written and run by software developers to ensure that code meets its design and behaves as intended.

http://en.wikipedia.org/wiki/Unit_testing

Benefits

The goal of unit testing is to isolate each part of the program and show that the individual parts are correct.[1] A unit test provides a strict, written contract that the piece of code must satisfy. As a result, it affords several benefits.

http://en.wikipedia.org/wiki/Unit_testing

In test-driven development (TDD), which is frequently used in both Extreme Programming and Scrum, unit tests are created before the code itself is written. When the tests pass, that code is considered complete. The same unit tests are run against that function frequently as the larger code base is developed either as the code is changed or via an automated process with the build. If the unit tests fail, it is considered to be a bug either in the changed code or the tests themselves. The unit tests then allow the location of the fault or failure to be easily traced. Since the unit tests alert the development team of the problem before handing the code off to testers or clients, it is still early in the development process.

http://en.wikipedia.org/wiki/Unit_testing

Unit testing allows the programmer to refactor code at a later date, and make sure the module still works correctly (e.g., in regression testing). The procedure is to write test cases for all functions and methods so that whenever a change causes a fault, it can be quickly identified.

Readily available unit tests make it easy for the programmer to check whether a piece of code is still working properly.

In continuous unit testing environments, through the inherent practice of sustained maintenance, unit tests will continue to accurately reflect the intended use of the executable and code in the face of any change. Depending upon established development practices and unit test coverage, up-to-the-second accuracy can be maintained.

http://en.wikipedia.org/wiki/Unit_testing

Unit testing may reduce uncertainty in the units themselves and can be used in a bottom-up testing style approach. By testing the parts of a program first and then testing the sum of its parts, integration testing becomes much easier.[citation needed]

An elaborate hierarchy of unit tests does not equal integration testing. Integration with peripheral units should be included in integration tests, but not in unit tests.[citation needed] Integration testing typically still relies heavily on humans testing manually; high-level or global-scope testing can be difficult to automate, such that manual testing often appears faster and cheaper.

http://en.wikipedia.org/wiki/Unit_testing

Unit testing provides a sort of living documentation of the system. Developers looking to learn what functionality is provided by a unit, and how to use it, can look at the unit tests to gain a basic understanding of the unit's interface (API).

Unit test cases embody characteristics that are critical to the success of the unit. These characteristics can indicate appropriate/inappropriate use of a unit as well as negative behaviors that are to be trapped by the unit. A unit test case, in and of itself, documents these critical characteristics, although many software development environments do not rely solely upon code to document the product in development.

http://en.wikipedia.org/wiki/Unit_testing

When software is developed using a test-driven approach, the combination of writing the unit test to specify the interface plus the refactoring activities performed after the test is passing, may take the place of formal design. Each unit test can be seen as a design element specifying classes, methods, and observable behaviour.

http://en.wikipedia.org/wiki/Unit_testing

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