A unit test is a test for a specific unit. Ideally, each http://en.wikipedia.org/wiki/Test_case - test case is independent from the others; http://en.wikipedia.org/wiki/Mock_object - mock objects http://en.wikipedia.org/wiki/Test_harness - test harnesses can be used to assist testing a module in isolation. Unit testing is typically done by the http://en.wikipedia.org/wiki/Software_developer - developers http://en.wikipedia.org/wiki/End-user - end-users . and and not by

Unit testing allows the programmer to http://en.wikipedia.org/wiki/Refactoring - refactor code at a later date, and make sure the module still works correctly (i.e. http://en.wikipedia.org/wiki/Regression_testing - regression testing ). The procedure is to write test cases for all http://en.wikipedia.org/wiki/Subroutine - functions and http://en.wikipedia.org/wiki/Method_%28computer_science%29 - methods so that whenever a change causes a regression, it can be quickly identified and fixed. This provides the benefit of encouraging programmers to make changes to the code since it is easy for the programmer to check if the piece is still working properly. Good unit test design produces test cases that http://en.wikipedia.org/wiki/Code_coverage - cover all paths through the unit with attention paid to loop conditions.

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.

Simplifies integration

Unit testing helps to eliminate uncertainty in the units themselves and can be used in a http://en.wikipedia.org/wiki/Top-down_and_bottom-up_design - bottom-up testing style approach. By testing the parts of a program first and then testing the sum of its parts, http://en.wikipedia.org/wiki/Integration_testing - integration testing becomes much easier.

A heavily debated matter exists in assessing the need to perform manual integration testing. While an elaborate hierarchy of unit tests may seem to have achieved integration testing, this presents a false sense of confidence since integration testing evaluates many other objectives that can only be proven through the human factor. Some argue that given a sufficient variety of test http://en.wikipedia.org/w/index.php?title=Automation_systems&action=edit - automation systems , integration testing by a human test group is unnecessary. Realistically, the actual need will ultimately depend upon the characteristics of the product being developed and its intended uses. Additionally, the human or manual testing will greatly depend on the availability of resources in the organization.