c# - Moq, strict vs loose usage

Question

In the past, I have only used Rhino Mocks, with the typical strict mock. I am now working with Moq on a project and I am wondering about the proper usage.

Let's assume that I have an object Foo with method Bar which calls a Bizz method on object Buzz.

In my test, I want to verify that Bizz is called, therefore I feel there are two possible options:

With a strict mock

var mockBuzz= new Mock<IBuzz>(MockBehavior.Strict);
mockBuzz.Setup(x => x.Bizz()); //test will fail if Bizz method not called
foo.Buzz = mockBuzz
foo.Bar();
mockBuzz.VerifyAll();

With a loose mock

var mockBuzz= new Mock<IBuzz>();    
foo.Buzz = mockBuzz
foo.Bar();
mockBuzz.Verify(x => x.Bizz()) //test will fail if Bizz method not called

Is there a standard or normal way of doing this?

Answer 1

I used to use strict mocks when I first starting using mocks in unit tests. This didn't last very long. There are really 2 reasons why I stopped doing this:

1. The tests become brittle - With strict mocks you are asserting more than one thing, that the setup methods are called, AND that the other methods are not called. When you refactor the code the test often fails, even if what you are trying to test is still true.
2. The tests are harder to read - You need to have a setup for every method that is called on the mock, even if it's not really related to what you want to test. When someone reads this test it's difficult for them to tell what is important for the test and what is just a side effect of the implementation.

Because of these I would strongly recommend using loose mocks in your unit tests.