How to use Mockito.mockStatic for mocking static methods in kotlin android

Question

How to use Mockito.mockStatic for mocking static methods in kotlin android ?

This is my code:

    class MyUtilClassTest {
       @Test
       fun testIsEnabled() {
          Mockito.mockStatic(MyUtilClass::class.java, Mockito.CALLS_REAL_METHODS)
                .use { mocked ->
                    mocked.`when`<Boolean> { MyUtilClass.isEnabled() }.thenReturn(true)
                    assertTrue(MyUtilClass.isEnabled())
                }
       }
    }
    
    object MyUtilClass {
       fun isEnabled(): Boolean = false
    }

I am getting this exception:

org.mockito.exceptions.misusing.MissingMethodInvocationException: when() requires an argument which has to be 'a method call on a mock'. For example: when(mock.getArticles()).thenReturn(articles);

Also, this error might show up because:

1. you stub either of: final/private/equals()/hashCode() methods. Those methods cannot be stubbed/verified. Mocking methods declared on non-public parent classes is not supported.
2. inside when() you don't call method on mock but on some other object.

Answer 1

If you annotate your function isEnabled with @JvmStatic, you won't get any error. As @Neige pointed out, static functions in Kotlin are actually not static in bytecode by default. Therefore, we need to mark our function with @JvmStatic in order to generate additional static getter/setter methods.

object MyUtilClass {
   @JvmStatic
   fun isEnabled(): Boolean = false
}