I would like to perform a junit test using Mockito on the toEntity function.
@Component
public class MyEntityTransform {
public Function<MyDTO , MyEntity> toEntity = new Function<MyDTO , MyEntity >() {
@Override
public MyEntity apply(MyDTO record) {
return new MyEntity();
}
};
}
Unfortunately the toEntity is NULL when I mock the class and I don't know how I can test it correctly.
@RunWith(MockitoJUnitRunner.class)
public class MyTest {
@InjectMocks
private MyService _classUnderTest;
@Mock
private MyEntityTransform myEntityTransform
@Before
public void setUp() {
Mockito.when(this.myEntityTransform.toEntity.apply(Mockito.anyObject())).thenReturn(...);
}
}
When I RUN the JUNIT test, Mockito give me the error :
java.lang.NullPointerException
org.mockito.exceptions.misusing.InvalidUseOfMatchersException:
Misplaced argument matcher detected here:-> at com.example.MyTest.setUp(MyTest.java:38)
You cannot use argument matchers outside of verification or stubbing.
Examples of correct usage of argument matchers:
when(mock.get(anyInt())).thenReturn(null);
doThrow(new RuntimeException()).when(mock).someVoidMethod(anyObject());
verify(mock).someMethod(contains("foo"))Also, this error might show up because you use argument matchers with
methods that cannot be mocked. Following methods cannot be
stubbed/verified: final/private/equals()/hashCode(). Mocking methods
declared on non-public parent classes is not supported.
Do you have suggestions?
Best Answer
You're using public fields, which is not a good idea. But anyway, what you want to mock is the function, not the instance of MyEntityTransform. So you would need something like
But quite frankly, I wouldn't use a public field of type Function. Instead, I would use a public method:
Then you can mock MyEntityTransform and make its toEntity method return what you want. And if you need to pass a Function doing what the method does, use a method reference: