Powermock mocking void method throws error

Question

I am using Powermockito, mockito with TestNG. My test class extends PowerMockTestCase. I want to mock a void method. For that I used following sample syntax,

@PrepareForTest(TestClass.class)
class Sample extends PowerMockTestCase{

@BeforeClass
public void beforeClass(){
TestClass obj = PowerMockito.spy(TestClass.getInstance());
PowerMockito.doNothing().when(obj).voidMethodName(Matchers.any(Type1.class), Matchers.anyString(), Matchers.any(Type2.class));
}

When I give this, I get :

FAILED CONFIGURATION: @BeforeClass beforeClass
org.mockito.exceptions.misusing.UnfinishedStubbingException: 
Unfinished stubbing detected here:
-> at org.powermock.api.mockito.internal.PowerMockitoCore.doAnswer(PowerMockitoCore.java:36)

E.g. thenReturn() may be missing.
Examples of correct stubbing:
    when(mock.isOk()).thenReturn(true);
    when(mock.isOk()).thenThrow(exception);
    doThrow(exception).when(mock).someVoidMethod();
Hints:
 1. missing thenReturn()
 2. you are trying to stub a final method, you naughty developer!

Can you please let me know what I am missing here?

Thanks

Answer 1

If the void method is not a final method, you do not need to use PowerMockito! Also, I don't see why you would mock "doNoting()". This would be used if you had a default mocking behavior, throwing an exception when the void method is called, and when for a specific test case you would want to override this behavior. Ib your case, would remove this line completely.