Mockito: You cannot use argument matchers outside of verification or stubbing I am trying to run the following simple test in Kotlin using Junit4 and Mockito open class B { lateinit var a: A public fun bFun(value: Int) : Int { return a.aFun(value) } } @ExtendWith(MockitoExtension::class) @RunWith(SpringJUnit4ClassRunner::class) class TestB { @Mock lateinit var a: A @InjectMocks lateinit var b: B @Test fun testB() { `when`(a.aFun(eq(1))).thenReturn(2) assertThat(b.bFun(1) == 2) } } However, I am...