使用InjectMocks错误的PowerMockito

Question

我有一个非常复杂的类来编写Junit测试用例。我决定使用PowerMockito，因为要为其运行测试的类具有构造函数初始化。

我的主课是这样的：

public class MainClass extends BaseClass{

MainClass(SomeClass class){
    super(class);
}

public void methodToBeTested(){
some code here
}

..few other methods which I am not going to test.
}

@RunWith(PowerMockRunner.class)
public class TestClass{

@Mock
OtherClassUsedInMainClass mock1;

@Mock
OtherClassUsedInMainClass mock2;

@InjectMocks
MainClass mainClass;

@Before
public void setUp() throws Exception{
    MockitoAnnotations.initMocks(this);
    PowerMockito.whenNew(MainClass.class).withArguments(Mockito.any(SomeClass.class))
            .thenReturn(mainClass);)
}

@Test
public void testMethodtobeTested(){
    ...I am using the other objects to mock data and test if this method works fine

    mainClass.methodtobeTested();
    \\This method will increment a value. I am just asserting if that value is right. 
    Assert.assertEquals(mainClass.checkCount(),RequiredCount)

}

}

org.mockito.exceptions.base.MockitoException: 
Cannot instantiate @InjectMocks field named 'mainClass' of type 'class com.main.MainClass'.
You haven't provided the instance at field declaration so I tried to construct the instance.
However the constructor or the initialization block threw an exception : null

Caused by: java.lang.NullPointerException
This null pointer exception is thrown from a the constructor of the BaseClass when it tries to initialize another class.

Answer 1

这个问题解释了@mock和@injectmocks之间的区别：

@mock创建一个mock。@injectmocks创建类的实例，并将使用@mock（或@spy)注释创建的mocks注入到该实例中。

MainClass构造函数需要一个SomeClass参数，但是没有任何模拟。

您的代码应该类似于：

@RunWith(PowerMockRunner.class)
public class TestClass{

    @Mock(answer = Answers.RETURNS_DEEP_STUBS)
    SomeClass mock1;

    @InjectMocks
    MainClass mainClass;

    @Before
    public void setUp() throws Exception{
    ...