Mockito's argThat returning null when in Kotlin

问题

Given the following class (written in kotlin):

class Target {
     fun <R> target(filter: String, mapper: (String) -> R): R = mapper(filter)
}

I'm able to test in java, the test code:

@Test
public void testInJava() {
    Target mockTarget = Mockito.mock(Target.class);
    Mockito.when(mockTarget.target(
            argThat(it -> true),
            Mockito.argThat(it -> true)
    )).thenReturn(100);
    assert mockTarget.target("Hello World", it -> 1) == 100;
}

The java test pass as expected, but the same test is written in kotlin:

@Test
fun test() {
    val mockTarget = Mockito.mock(Target::class.java)
    Mockito.`when`(mockTarget.target(
            Mockito.argThat<String> { true },
            mapper = Mockito.argThat<Function1<String, Int>>({ true }))
    ).thenReturn(100)
    assert(mockTarget.target("Hello World") { 1 } == 100)
}

The kotlin version I receive the following exception:

java.lang.IllegalStateException: Mockito.argThat<String> { true } must not be null

Why is it happening and how can I test that using kotlin?

回答1:

I also faced the same problem.

And finally, I found argThat() will return null, and normally the argument in the function in kotlin, does not accept null type.

So when we mock the function, it will throw IllegalStateException, because argThat returns null and argument can't be null.

My solution is to define the argument with class? so that it can accept null, but I don't know if it is a great solution

来源：https://stackoverflow.com/questions/52389727/mockitos-argthat-returning-null-when-in-kotlin

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java

kotlin

mockito