mockito - how to check an instance inside a method

Question

I am new to Mockito, I am trying to verify the attributes of an object which gets created inside a method.

pseudo code below:

class A{
   ...    
   public String methodToTest(){
       Parameter params = new Parameter(); //param is basically like a hashmap
       params.add("action", "submit");
       return process(params);
   }
   ...
   public String process(Parameter params){
       //do some work based on params 
       return "done";  
   }
}

I want to test 2 things:

1. when I called methodToTest, process() method is called

2. process() method is called with the correct params containing action "submit"

I was able to verify that process() is eventually called easily using Mockito.verify(). However trying to check that params contains action "submit" is very difficult so far.

I have tried the following but it doesn't work :(

BaseMatcher<Parameter> paramIsCorrect = new BaseMatcher<Parameter>(){
    @Overrides
    public boolean matches(Object param){
        return ("submit".equals((Parameter)param.get("action")));
    }

    //@Overrides description but do nothing
}

A mockA = mock(A);
A realA = new A();
realA.methodToTest();
verify(mockA).process(argThat(paramIsCorrect))

Any suggestion ?

Answer 1

Just pass Parameter in as a constructor argument to a constructor of the class A, then use a mocked instance/implementation of Parameter in your test and verify on the mock. That is how it is normally done - you separate your classes and compose them using constructor injection, that enables you to pass in mocks for testing purposes (it also allows rewiring the application and exchanging some commons a lot easier).

If you need to create Parameter on every function invocation you should use a factory that creates Parameter instances and pass that in. Then you can verify on the factory as well as the object created by the factory.

Answer 2

If you have got verify() to work, presumably it is just a case of using an argument matcher to check the contains of params.

http://docs.mockito.googlecode.com/hg/org/mockito/Mockito.html#3

The example given in the above docs is verify(mockedList).get(anyInt()). You can also say verify(mockedList).get(argThat(myCustomMatcher)).

As an aside, it sounds like you are mocking the class under test. I've found that this usually means I haven't thought clearly about either my class or my test or both. In your example, you should be able to test that methodToTest() returns the right result irrespective of whether or not it calls process() because it returns a String. The mockito folk have lots of good documentation about this sort thing, particularly the "monkey island" blog: http://monkeyisland.pl/.