java - 调用验证伴随对象方法的单元测试(模拟伴随对象)

Question

当切换到 Kotlin 时，静态方法被移动到伴随对象中。但是，没有明显的方法可以对调用这些“静态方法”的其他方法进行单元测试。

在 Java 中，我们可以使用 PowerMockito 的 MockStatic(SomeClass.class) 来验证在被测方法中调用了静态方法。 PowerMock 在 Kotlin 中失去了它的魔力。

为了测试，我创建了以下类。

public class DummyJava {
    static public Void staticMechod(){
          System.out.print("Dummy method is called");
          return null;
     }
}

class DummyCompanion {
    companion object {
        fun someCompanionMethod(){
            System.out.printf("companion method is called\n")
        }
    }
}

现在有另一个类调用 DummyCompanion.someCompanion

public class DummyWrapper {
    public void callAStaticMethod(){
        DummyJava.staticMechod();
    }

    public void callCompanionMethod(){
        DummyCompanion.Companion.someCompanionMethod();
    }
}

单元测试callAStaticMethod()我们使用了下面的

@RunWith(PowerMockRunner.class)
@PrepareForTest({DummyJava.class, DummyCompanion.Companion.class})
public class staticClassTest {
    //This case works
    @Test 
    public void testForStaticMethod() {
        PowerMockito.mockStatic(DummyJava.class);   
        DummyWrapper testObject = new DummyWrapper();

        Mockito.when(DummyJava.staticMechod()).thenCallRealMethod();

        testObject.callAStaticMethod();

        PowerMockito.verifyStatic(Dummy.class);
        DummyJava.staticMechod();
    }

    //This case doesn't work. It always passes.
    @Test
    public void testForCompanionMethod() {
        PowerMockito.mockStatic(DummyCompanion.Companion.class);
        DummyWrapper testObject = new DummyWrapper();
        testObject.callCompanionMethod();
PowerMockito.verifyStatic(DummyCompanion.Companion.class,Mockito.times(1));
        DummyCompanion.Companion.someCompanionMethod();
}

我的问题是如何验证配套方法是否被调用。

Answer 1

方案一:在调用类中添加调用函数

public class DummyWrapper {
val foo get() = DummyCompanion.Companion

public void callAStaticMethod(){
    foo.staticMechod();
}

public void callCompanionMethod(){
    foo.someCompanionMethod();
}
}

在测试类中，我们可以使用 Mockito 为 get() 函数提供 stub 并验证它是否被调用。

@Test
fun testCase{
....
val mockCompanionObj: DummyCompanion.Companion = mock()
val wrapper = DummyWrapper()

whenever(wrapper.foo).thenReturn(mockCompanionObj)
wrapper.callCompanionMethod()
verify(mockCompanionObj).someCompanionMethod()
....
}

方案二:使用Mockk在 Mockk 中模拟伴生对象很容易。无需在源代码中插入测试接口(interface)对象。

 @Test
 fun testCompanionObject() {
    //Mock the companion object
    mockkObject(DummyCompanion.Companion)

    //define the stubbing bechavior of a companion object method
    every { DummyCompanion.Companion.companionMethod() } answers { stubMethod() }

    val testObject = DummyWrapper()

    //Call a method that calls the companion object method
    //You can verify stubMethod() is called
    testObject.callCompanionMethod()

    verify(exactly = 1) { DummyCompanion.someCompanionMethod() }
}

有关详细信息，请参阅 Mockk