Using PowerMock to mock a private method called in the constructor of the class under test

Question

I don't know if this is possible with Powermock. I need to use Powermock to mock a private method that is called in the constructor of the class that I need to test. So I have a test class like this:

@RunWith(PowerMockRunner.class)
@PrepareForTest(XMLTransaction.class)
public class CloseSummaryOrCloseTrailerResponseTest {
    public final static String URL="WL_APPSERVER";
    private XMLTransaction xmlTransaction; 

    @Before
    public void initMocks() throws Exception {
        xmlTransaction = PowerMockito.spy(new XMLTransaction(URL)); 
        PowerMockito.doAnswer(new org.mockito.stubbing.Answer<Object>() {
            @Override
            public Object answer(InvocationOnMock invocation) throws Throwable {
                return null; //does nothing
            }
        }).when(xmlTransaction.getClass(), "initialize");
        PowerMockito.doNothing().when(xmlTransaction.getClass(), "initialize");             
    }

    @Test
    public void whenCloseSummaryResponseNoErrorExpectCorrectXmlMsgProduced () throws Exception
    {
    //set the mock object here
        try {                    
            String actualXmlScannerMsg = xmlTransaction.closeSummaryResponseToXMLNoErrors(mockCloseTrailerResponse);
            Assert.assertNotNull(actualXmlScannerMsg);
            Assert.assertEquals(msgNoCarReturnCharCloseSummaryResponse, actualXmlScannerMsg);   
        }
        catch(JsonProcessingException jEx)
        {
            Assert.fail("JsonProcessingException: " + jEx.getMessage());
        }
        catch(Exception ex)
        {
            Assert.fail("Exception occurred: " + ex.getMessage());
        }
    }
}

I get a null pointer exception when creating the spy. The constructor new XMLTransaction(URL) calls the initialize method which is the method I want to do nothing.

Is there any way to get around this problem. If I use the default constructor, the class is not created.

Answer 1

I figured this out... I created a default constructor and set all of the classes instantiated in the initialize method to null. Removed this from initMock()

PowerMockito.doAnswer(new org.mockito.stubbing.Answer<Object>() {
            @Override
            public Object answer(InvocationOnMock invocation) throws Throwable {
                return null; //does nothing
            }
        }).when(xmlTransaction.getClass(), "initialize");
        PowerMockito.doNothing().when(xmlTransaction.getClass(), "initialize");