Kotlin: Manually inlining a generic function produ

问题:

I have a simple test class

class SimpleClassTest {

    private fun <T> anyObject(): T {
        return Mockito.anyObject<T>()
    }

    lateinit var simpleObject: SimpleClass
    @Mock lateinit var injectedObject: InjectedClass


    @Before
    fun setUp() {
        MockitoAnnotations.initMocks(this)
    }

    @Test
    fun testSimpleFunction() {
        simpleObject = SimpleClass(injectedObject)
        simpleObject.simpleFunction()

        verify(injectedObject).settingDependentObject(anyObject())
    }
}

It works fine and pass.

Since the private generic anyObject() function is only used once, so I decide to inlining it (manually) i.e. remove the need of that function, whereby I change from

verify(injectedObject).settingDependentObject(anyObject())

to

verify(injectedObject).settingDependentObject(Mockito.anyObject<DependentClass>())

However this now error as java.lang.IllegalStateException: Mockito.anyObject<DependentClass>() must not be null

Anything I did wrong inlining the function call to a direct statement?

Is there anything different between using

private fun <T> anyObject(): T {
    return Mockito.anyObject<T>()
}

and the below?

Mockito.anyObject<DependentClass>()

回答1:

The source for Mockito.anyObject():

/**
 * Matches anything, including null.
 * <p>
 * This is an alias of: {@link #any()} and {@link #any(java.lang.Class)}
 * <p>
 * See examples in javadoc for {@link Matchers} class
 * 
 * @return <code>null</code>.
 */
public static <T> T anyObject() {
    return (T) reportMatcher(Any.ANY).returnNull();
}

This method sets some internal state for Mockito, and then proceeds to return null. Since you're expecting a non-null instance in your settingDependentObject() method, the runtime fails.

---

Why your first method succeeded, however, I'm not sure. Casting null to T seemed to work a while ago, but it doesn't work for me anymore. For that matter, I can't get your first implementation to succeed either.