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.
Test cases can either be used to test logic or integration. Logical tests are used to validated (internal) classes and methods. Integration tests are intended to validated the public interfaces.