Objects annotated with Mockito annotations @Mock, @Spy, @Captor, or @InjectMocks
need to be initialized explicitly.
There are several ways to do this:
- Call
MockitoAnnotations.openMocks(this) or MockitoAnnotations.initMocks(this) in a setup method
- Annotate test class with
@RunWith(MockitoJUnitRunner.class) (JUnit 4)
- Annotate test class with
@ExtendWith(MockitoExtension.class) (JUnit 5 Jupiter)
- Use
@Rule public MockitoRule rule = MockitoJUnit.rule();
Test using uninitialized mocks will fail.
Note that this only applies to annotated Mockito objects. It is not necessary to initialize objects instantiated via Mockito.mock() or
Mockito.spy().
This rule raises an issue when a test class uses uninitialized mocks.
Noncompliant code example
public class FooTest { // Noncompliant: Mockito initialization missing
@Mock private Bar bar;
@Spy private Baz baz;
@InjectMocks private Foo fooUnderTest;
@Test
void someTest() {
// test something ...
}
@Nested
public class Nested {
@Mock
private Bar bar;
}
Compliant solution
@RunWith(MockitoJUnitRunner.class)
public class FooTest {
@Mock private Bar bar;
// ...
}
@ExtendWith(MockitoExtension.class)
public class FooTest {
@Mock private Bar bar;
// ...
}
public class FooTest {
@Rule
public MockitoRule rule = MockitoJUnit.rule();
@Mock private Bar bar;
// ...
}
public class FooTest {
@Mock private Bar bar;
// ...
@BeforeEach
void setUp() {
MockitoAnnotations.openMocks(this);
}
// ...
}
public class FooTest {
@Mock private Bar bar;
// ...
@Before
void setUp() {
MockitoAnnotations.initMocks(this);
}
// ...
}
@ExtendWith(MockitoExtension.class)
public class FooTest {
@Nested
public class Nested {
@Mock
private Bar bar;
}
}
