How to mock private method using Power Mockito?

Question

I am trying to mock my private method , but I am getting java.lang.IllegalArgumentException: object is not an instance of declaring class .Below is my method

private String decodeResponse(byte bresp[])
    {

        String spresp = null;
        //
        return spresp;
    }

Below is my test class ,

@PrepareForTest(MyClass.class)
    @RunWith(PowerMockRunner.class)
    public class MyClassTest{

    @Test
    public void test() throws Exception {
        PowerMockito.spy(MyClass.class);
        PowerMockito.doReturn("abcdefg").when(MyClass.class, "decodeResponse",Matchers.anyByte());
    }   
    }

I am stuck in this issue for past 3 hours . Any help will be highly appreciable.

Answer 1

    @PrepareForTest(MyClass.class)
    @RunWith(PowerMockRunner.class)
    public class MyClassTest{

    @Test
    public void test() throws Exception {
        MyClass myClassSpy = PowerMockito.spy(MyClass.class);
        PowerMockito.doReturn("abcdefg").when(myClassSpy, "decodeResponse",any(byte[].class));
    }   
    }