java - Mockito无法实例化被测类

Question

我有三个类A、B和C:

public class A {
  @Autowired
  private B someB;
  private C someC = someB.getSomeC();
}

@Service
public class B {
  C getSomeC() {
    return new C();
  }
}

public class C { }

现在，如果我为 A 编写一个单元测试，如下所示:

@RunWith(MockitoJUnitRunner.class)
public class ATest {

  @InjectMocks
  private A classUnderTest;

  @Mock
  private B someB;

  @Mock
  private C someC;

  @Test
  public void testSomething() {

  }
}

Mockito 对此并不满意:

 org.mockito.exceptions.base.MockitoException: 
    Cannot instantiate @InjectMocks field named 'classUnderTest' of type 'class my.package.A'.
    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

如果我删除类 A 中的调用，则类 A 如下所示:

public class A {
  private B someB;
  private C someC;
}

，Mockito能够实例化UnderTest类并且测试运行通过。

为什么会出现这样的情况呢？

编辑:使用 Mockito 1.9.5

Answer 1

嗯，这总是会失败:

public class A {
  private B someB;
  private C someC = someB.getSomeC();
}

您尝试对一个始终为空的值调用getSomeC()...这将始终抛出NullPointerException。您需要修复 A 以更好地处理依赖关系。 (我个人会将它们作为构造函数参数，但当然还有其他选项......)