Concepts: Stages of Test

Testing is usually applied to different types of targets in different stages of the software's delivery cycle. These stages progress from testing small components (unit testing) to testing completed systems (system testing).

Unit Test

Unit test, implemented early in the iteration, focuses on verifying the smallest testable elements of the software. Unit testing is typically applied to components in the implementation model to verify that control flows and data flows are covered and function as expected. These expectations are based on how the component participates in executing a use case, which you find from sequence diagrams for that use case. The Implementer performs unit test as the unit is developed. The details of unit test are described in the Implementation workflow.

Integration Test

Integration testing is performed to ensure that the components in the implementation model operate properly when combined to execute a use case. The target-of-test is a package or a set of packages in the implementation model. Often the packages being combined come from different development organizations. Integration testing exposes incompleteness or mistakes in the package's interface specifications.

System Test

System testing is done when the software is functioning as a whole, or when well-defined subsets of its behavior are implemented. The target, in this case, is the whole implementation model for the system.