java - 如何使用 Mockito JUNIT java.util.Function

Question

我想使用 Mockito 对 toEntity 函数执行 junit 测试。

    @Component
    public class MyEntityTransform {
        public Function<MyDTO , MyEntity> toEntity = new Function<MyDTO , MyEntity >() {
            @Override
            public MyEntity apply(MyDTO record) {
                return new MyEntity();
            }
        };  
    }

不幸的是，当我模拟该类时，toEntity 为NULL，并且我不知道如何正确测试它。

@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(...);
    }   
}

当我运行 JUNIT 测试时，Mockito 给出错误:

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.

你有什么建议吗？

Answer 1

您正在使用公共(public)字段，这不是一个好主意。但无论如何，您想要模拟的是函数，而不是 MyEntityTransform 的实例。所以你需要类似的东西

@InjectMocks
private MyService _classUnderTest;

@Mock // or @Spy
private MyEntityTransform myEntityTransform;

@Before
public void prepare() {
    myEntityTransform.toEntity = mock(Function.class);
}

但坦率地说，我不会使用 Function 类型的公共(public)字段。相反，我会使用公共(public)方法:

public class MyEntityTransform {
    public MyEntity toEntity(MyDTO record) {
        return new MyEntity();   
    }
}

然后你可以模拟 MyEntityTransform 并使其 toEntity 方法返回你想要的内容。如果您需要传递一个函数来执行该方法的操作，请使用方法引用:

collection.stream().map(myEntityTranform::toEntity)