How to test that method was called inside another method

Question

I've got some ugly class to test, then i have to admit that I can't modify it. So let's go to base of the problem.

I've got a class, with one pretty long static method, like this:

public class SomeClass{

public SomeClass(){
}

public static String Dispatch(HttpServletRequest request){
    String param1= request.getParameter("param1");
    String param2 = request.getParameter("param2");

    Factory factory = // .. some Bean, used as Factory

    // lot, lot if.. else statements that returning smth based on params  
    if(param1.equalsIgnoreCase("smthParam1")){
        if(param2.equalsIgnoreCase("smthParam2")){
            factory.getInstance().invokeSmth();
        } else if(param2.equalsIgnoreCase("smthParam2_2")){
            factory.getAnotherObjectInstance().invokeSmth();
        } else if(param2.equalsIgnoreCase("smthParam2_3")){
            factory.getYetAnotherObjectInstance().invokeSmth();
        }
    }

   // More if.. else statements...

    return "Error";
}

}

Then, I want to test that, if there is some request params it will invoke a Singleton method from factory.

I have no idea how to do that, Is it possible to do? Please remember that I can't change the original code. Thank's for help.

Answer 1

PowerMock may be able to help you. As I understand it the MockConstructor should do the trick. Following the example from the linked documentation, you should get something like this:

@RunWith(PowerMockRunner.class)
@PrepareForTest(SomeClass.class)
public class SomeClassTest {

    @Test
    public void testCreateDirectoryStructure_ok() throws Exception {
        // create parameters for factory creation
        Factory factoryMock = createMock(Factory.class);

        SomeClass tested = new SomeClass();

        expectNew(Factory.class, /* parameters */).andReturn(factoryMock);
        // mock factory methods
        replay(factoryMock, Factory.class);

        tested.Dispatch(/*...*/);

        // assert / verify interaction
    }
}