testingWithAndWithoutMocks.java

/*Example of how you can rewrite your code to avoid the need for mocks in your tests */


/*-----------------------------------------------
Implementation where you need mocks for testing
-------------------------------------------------*/
public class MyClassThatNeedsTesting {
    private BusinessLogicClass blc;
    
    public int estimatedTotalCost(SomeDataStructure input) {
        int size = input.something.size();
        int factor = size > 3 ? 1 : 1.5; 
        return size * a – b / blc.foo() + factor; 
        /* whatever – just some calculation worthy of testing that uses input from the business logic class */
    }
}

/*To test this you need to mock the BusinessLogicClass and specify what to return in the foo() method. */
public class MyClassThatNeedsTestingTest {
    
    public void should_do_the_right_thing() {
        MyClassThatNeedsTesting myTestObject = new MyClassThatNeedsTesting();
        BusinessLogicClass mock = mock(BusinessLogicClass.class);
        when(mock.foo()).thenReturn(5);
        assertEquals(10, myTestObject.estimatedTotalCost(formData);
    }
}


/*-----------------------------------------------
Implementation without need for mocks in testing
-------------------------------------------------*/
public class MyClassThatNeedsTesting {
    private BusinessLogicClass blc;
    
    public int estimatedTotalCost(MyFormData input) {
        return estimatdTotalCost(input.something.size(), blc.foo());
    }
    
    /* extracted the test-worthy stuff into a separate function that just takes the necessary parameters as input */
    int estimatedTotalCost(int size, int foo) {
        int factor = size > 3 ? 1 : 1.5;
        return size * a – b / foo + factor;
    }
}

/*Now you can test the implementation without mocking, just by sending whatever values for foo into the calculation function.  */
public class MyClassThatNeedsTestingTest {
    public void should_still_do_the_right_thing() {
        assertEquals(10, new MyClassThatNeedsTesting().estmatedTotalCost(3, 5);
    }
}

/* Much easier to test. No mocks required */