Testing private methods in java using Powermockito

Question

I am using PowerMockito and jUnit to write unit test cases.

public class Foo {
    private String resolveApplicationId() {
        return "testApplication";
    }
}

Here is my test case

@RunWith(PowerMockRunner.class)
@PrepareForTest(Foo.class)
public class test{

@Before
    public void prepareTest() {
        foo = PowerMockito.spy(new Foo());
    }
@Test
public void checkApplicationIdIsResolved() throws Exception {
    PowerMockito.doNothing().when(foo, "myPrivateMethod");
    PowerMockito.verifyPrivate(foo).invoke("myPrivateMethod");
//Assert Here the returned value
}

}

Please tell me

 1. how can I assert the value returned by the method when it is called
 2. how can I call the private method
 3. if not then what actually I verify when I write test case for private methods.

Thanks.

Have you read this http://stackoverflow.com/questions/34571/whats-the-proper-way-to-test-a-class-with-private-methods-using-junit? — Roman-Stop RU aggression in UA, Feb 21 '14 at 15:55
No but I read the post. However the post does not answer my question. It is more particular about writing junits for private methods using PowerMockito. — Amit Kumar, Feb 24 '14 at 10:01

score 1 · Accepted Answer · edited May 23 '17 at 12:08

Testing private method does not differ from testing public method. If there is no external dependencies you even don't need to create and use any mocks. The only problem is with invocation of the private method from test. This is described here or you may use spring utils.

So you don't need to mock the method you are testing. You only require to mock other objects which are not tested in this particular test. So you test would look like

@Test
public void checkApplicationIdIsResolved() throws Exception {
    // makeResolveIdAccessible();
    // if needed setup mocks for objects used in resolveApplicationId 
    assertEquals(expectedApplicationId, foo.resolveApplicationId())
}

Testing private methods in java using Powermockito

1 Answers1