Test case

This article is about test cases in software engineering. For test cases in Case law, please check the appropriate article

In software engineering, the most common definition of a test case is a set of conditions or variables under which a tester will determine if a requirement or use case upon an application is partially or fully satisfied. It may take many test cases to determine that a requirement is fully satisfied. In order to fully test that all the requirements of an application are met, there must be at least one test case for each requirement unless a requirement has sub requirements. In that situation, each sub requirement must have at least one test case. This is frequently done using a traceability matrix. Some methodologies, like RUP, recommend creating at least two test cases for each requirement. One of them should perform positive testing of requirement and other should perform negative testing. Written test cases should include a description of the functionality to be tested, and the preparation required to ensure that the test can be conducted.

If the application is created without formal requirements, then test cases can be written based on the accepted normal operation of programs of a similar class. In some schools of testing, test cases are not written at all but the activities and results are reported after the tests have been run.

What characterizes a formal, written test case is that there is a known input and an expected output, which is worked out before the test is executed. The known input should test a precondition and the expected output should test a postcondition.

Under special circumstances, there could be a need to run the test, produce results, and then a team of experts would evaluate if the results can be considered as a pass. This happens often on new products' performance number determination. The first test is taken as the base line for subsequent test / product release cycles.

Written test cases are usually collected into test suites.

A variation of test cases are most commonly used in acceptance testing. Acceptance testing is done by a group of end-users or clients of the system to ensure the developed system meets their requirements. User acceptance testing is usually differentiated by the inclusion of happy path or positive test cases.

Structure of test case

Formal, written test cases consist of three main parts with subsections:

• Information contains general information about Test case.
  • Identifier is unique identifier of test case for further references, for example, while describing found defect.
  • Test case owner/creator is name of tester or test designer, who created test or is responsible for its development
  • Version of current Test case definition
  • Name of test case should be human-oriented title which allows to quickly understand test case purpose and scope.
  • Identifier of the requirement which is covered by the test case. Also here could be an identifier of a use case or a functional specification item.
  • Purpose contains short description of test purpose, what functionality it checks.
  • Dependencies
• Test case activity
  • Testing environment/configuration contains information about configuration of hardware or software which must be met while executing test case
  • Initialization describes actions, which must be performed before test case execution is started. For example, we should open some file.
  • Finalization describes actions to be done after test case is performed. For example if test case crashes database, tester should restore it before other test cases will be performed.
  • Actions step by step to be done to complete test.
  • Input data description
• Results
  • Expected results contains description of what tester should see after all test steps has been completed
  • Actual results contain a brief description of what the tester saw after the test steps has been completed. This is often replaced with a Pass/Fail. Quite often if a test case fails, reference to the defect involved should be listed in this column.

Not all written tests require all of these sections. However, the bare bones of a test can be reduced to three essential steps:

• Establish the preconditions
• Exercise the item under test
• Verify the postconditions

It is important to note that if the preconditions cannot be established, the item cannot be tested according to its software requirements specification and the test must not proceed.

Verifying the postcondition is equivalent to establishing that the actual results are as expected.

Note that several tests may need to be run to challenge the postcondition. For example, to test a user login routine would need at least a case of a known username-password pair and a second case of an unknown user name-password pair.

See also

• Software testing
• Acceptance testing
• Bug Report

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