Mockito Argument Matcher any() - Argument(s) are different! for verify method called with any()

Question

I am trying to write a test where I am very simply checking if a method was called on a mock. Should be easy, I've done it many times using verify, however for some reason my test is failing because it seems to be comparing the actual invocation arguments to <any Type>.

My code:

val mockSearchApi = mock<SearchApi>()
whenever(mockSearchApi.searchBrands(any(), any(), any(), any(), any(), any(), any(), any()))
     .thenReturn(Single.just(getSearchApiResponse()))

// Some code that causes the api .searchBrands to get called

verify(mockSearchApi, times(1)).searchBrands(any(), any(), any(), any(), any(), any(), any(), any())

Then the test fails with error

Argument(s) are different! Wanted:
searchApi.searchBrands(
    <any java.lang.Boolean>,
    <any java.util.List>,
    <any java.lang.Integer>,
    <any java.lang.Integer>,
    <any java.lang.String>,
    <any java.lang.String>,
    <any java.lang.Boolean>,
    <any java.util.Map>
);
-> at ...
Actual invocations have different arguments:
searchApi.searchBrands(
    false,
    [],
    1,
    null,
    null,
    null,
    true,
    {}
);

So the method is called and the argument types are correct, so why does this fail?

And I have also tried changing all of those any() calls to anyBoolean(), anyList(), anyString(), etc. and the same happens. I have also ensured that the code is calling the arguments in the right order as I've seen that issue before with mocks as well.

Answer 1

Most likely you used any() from mockito-kotlin

Original ArgumentMatchers behaviour:

• any() - Matches anything, including nulls and varargs.
• any​(Class<T> type) - Matches any object of given type, excluding nulls.
• both functions return null

To prevent exception when null is returned, mockito-kotlin changes this behaviour. See Matchers.kt

/** Matches any object, excluding nulls. */
inline fun <reified T : Any> any(): T {
    return ArgumentMatchers.any(T::class.java) ?: createInstance()
}

/** Matches anything, including nulls. */
inline fun <reified T : Any> anyOrNull(): T {
    return ArgumentMatchers.any<T>() ?: createInstance()
}

mockito-kotlin matchers behaviour:

• any() delegates to ArgumentMatchers.any(T::class.java) and thus does not match nulls
• anyOrNull() delegates to ArgumentMatchers.any<T>() and thus matches null