Rhino Mocks

If you give a Rhino a cookie…

There is a book that I use to read to my daughter titled “If You Give a Mouse a Cookie.” It’s a funny book which takes the reader through a circular pattern of what happens if you give a mouse a cookie. My daughter would often wait till the end of the story to ask what happened next. In my mind this was a clever attempt to have me read the book again (and again). There were sometimes, however, I would re-read the story; especially after a loving “pleeaaassseeee”

As I have been “healing” the existing unit tests, this book came to mind as I begin to see a “circular pattern.” Granted this doesn’t produce anything wrong or exhibit poor code but… I can see where these “circular patterns” have lead to confusion and claims of Rhino Mocks being overly complex.

A good example of this can be found with the Expect and SetupResult utility classes versus the Expect extension method.

The Expect extension method was added as a part of the Arrange Act Assert (AAA) syntax. Since I prefer the AAA syntax, this is the method that I use the most. Let’s take a quick look at an example:

[Fact]
public void Test_One() {
  var mock = MockRepository.GenerateMock<ISomeClass>();

  mock.Expect(x => x.SayHello())
    .Return("Hello World");

  var hello = mock.SayHello();

  Assert.Equal("Hello World", hello);
  mock.VerifyAllExpectations();
}

Unfortunately there is nothing stopping a developer from using one of the other two approaches. The following two examples show how the Expect and SetupResult utility classes are (basically) interchangeable.

[Fact]
public void Test_Two() {
  var mock = MockRepository.GenerateMock<ISomeClass>();

  Expect.Call(mock.SayHello())
    .Return("Hello World");

  var hello = mock.SayHello();

  Assert.Equal("Hello World", hello);
  mock.VerifyAllExpectations();
}

[Fact]
public void Test_Three() {
  var mock = MockRepository.GenerateMock<ISomeClass>();

  SetupResult.For(mock.SayHello())
    .Return("Hello World");

  var hello = mock.SayHello();

  Assert.Equal("Hello World", hello);
  mock.VerifyAllExpectations();
}

What isn’t obvious, however, is that these two tests will fail. The two worlds simply don’t play nice together. It is true that they can co-exist and you could modify the tests above to make them pass but… is it worth it?

In other words, if you give a developer a cookie…

Rhino Mocks will be going on a diet and won’t be offering any more cookies. No matter how lovingly I hear “pleeaaassseeee”

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One thought on “If you give a Rhino a cookie…

  1. Pingback: Dew Drop – July 3, 2013 (#1,578) | Alvin Ashcraft's Morning Dew

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