MockK

The toolkit is provided as a set of artifacts deployed to the Maven Central repository. It requires Java 7 or newer for test execution; tests must use JUnit or TestNG. For instructions on how to add the library to a Java project, see Running tests with JMockit. In this tutorial we examine the APIs available in the library, with the help of example tests (using Java 8). The central API - a single annotation - provides support for the automatic instantiation and initialization of the objects to be tested. Then we have the mocking API (also known as the "Expectations" API), intended for tests which use mocked dependencies. Finally, there is a small faking API (aka the "Mockups" API), which can be used for the creation and application of fake implementations that avoid the full cost of external components.

Writing unit tests can be hard and sometimes good design has to be sacrificed for the sole purpose of testability. Often testability corresponds to good design, but this is not always the case. For example final classes and methods cannot be used, private methods sometimes need to be protected or unnecessarily moved to a collaborator, static methods should be avoided completely and so on simply because of the limitations of existing frameworks. PowerMock is a framework that extends other mock libraries such as EasyMock with more powerful capabilities. PowerMock uses a custom classloader and bytecode manipulation to enable mocking of static methods, constructors, final classes and methods, private methods, removal of static initializers and more. By using a custom classloader no changes need to be done to the IDE or continuous integration servers which simplifies adoption.