Whitebox.getInternalState()

Similar to setInternalState() you can get value of any global field at my time with getInternalState() method.

This method is really useful to test any void methods, we can get any state change caused by that void method and write our assertion on that.

for example:

// Example Source Class
public class ExampleClass {

    private int mHeight = 0;

    public void clear() {
        // this is a void method that updated height and does not return anything.
        mHeight = 0;
    }
}

With method's like clear() that return void but change state of class, we can get value of mHeight and check if it was unset or not.

Here is how we would achieve that:

@RunWith(PowerMockRunner.class)
@PrepareForTest({
    ExampleClass.class
})
public class ExampleClassTest {

    private ExampleClass classUnderTest;

    @Before
    public void setUp() throws Exception {
        // Create constructor of ExampleClass
        classUnderTest = new ExampleClass();
    }

    @Test
    public void getHeight_shoudReturnHeightOfView() throws NoSuchMethodException {
        // Given

        // When
        classUnderTest.clear()

        // Then
        final int mHeight = Whitebox.getInternalState(classUnderTest, "mHeight");;
        Assert.assertEquals(0, mHeight);
    }
}