What is MockitoRule ?

memo.MD

The JUnit rule can be used instead of MockitoJUnitRunner. It requires JUnit at least 4.7. This rule adds following behavior: Initializes mocks annotated with Mock, so that explicit usage of MockitoAnnotations.initMocks(Object) is not necessary. Mocks are initialized before each test method. validates framework usage after each test method. See javadoc for Mockito.validateMockitoUsage().

Copy-paste from http://site.mockito.org/mockito/docs/current/org/mockito/junit/MockitoRule.html

Sample.java

 public class ExampleTest {

     @Rule
     public MockitoRule rule = MockitoJUnit.rule();

     @Mock
     private List list;

     @Test
     public void shouldDoSomething() {
         list.add(100);
     }
 }