Auto inject dependencies in JUnit using Mockito

While writing unit tests, you often have to mock dependencies like services or controllers. Often  a constructor is used to autowire the dependencies as shown in the example below. In the Test class I instantiated the ContactService using a contactRepository Mock object

The test class:

In the previous example you always have to Autowire the constructor and bind the dependencies to the class variables. In the next example the code is cleaner by autowiring the mocking objects, so you don’t have to create a custom constructor or setters to set the dependencies, which makes your code more concise and easier to read.

The test class:

Take a note of the “RunWith(MockitoJUnitRunner.class)” annotation. This annotation will initialize the annotated mock objects. An alternative is to use “MockitoAnnotations.initMocks(this)” in a setup method to initalize the annotated mock objects.

More tips can be found on the Mockito RefCard: or take a look at the mockito site: