UnitTest : Moq

What?

Moq (pronounced "Mock-you" or just "Mock") is the only mocking library for .NET developed from scratch to take full advantage of .NET 3.5 (i.e. Linq expression trees) and C# 3.0 features (i.e. lambda expressions) that make it the most productive, type-safe and refactoring-friendly mocking library available. And it supports mocking interfaces as well as classes. Its API is extremely simple and straightforward, and doesn't require any prior knowledge or experience with mocking concepts.

 Checkout the QuickStart for more examples!

 

Features at a glance

Moq offers the following features:

• Strong-typed: no strings for expectations, no object-typed return values or constraints
• Unsurpassed VS intellisense integration: everything supports full VS intellisense, from setting expectations, to specifying method call arguments, return values, etc.
• No Record/Replay idioms to learn. Just construct your mock, set it up, use it and optionally verify calls to it (you may not verify mocks when they act as stubs only, or when you are doing more classic state-based testing by checking returned values from the object under test)
• VERY low learning curve as a consequence of the previous three points. For the most part, you don't even need to ever read the documentation.
• Granular control over mock behavior with a simple MockBehavior enumeration (no need to learn what's the theoretical difference between a mock, a stub, a fake, a dynamic mock, etc.)
• Mock both interfaces and classes
• Override expectations: can set default expectations in a fixture setup, and override as needed on tests
• Pass constructor arguments for mocked classes
• Intercept and raise events on mocks
• Intuitive support for out/ref arguments 

Installing and Setting Up Moq

Moq is maintained as a Google Code project. You can download the Moq binaries and API documentation here:

http://code.google.com/p/moq/

After you download the Moq binaries from Google Code, make sure that you unblock the archive by right-clicking the file, selecting Properties, and pushing the Unblock button (see Figure 1). If you forget to do this, you run into confusing security issues when you try to use Moq within Visual Studio.

The archive includes an assembly named Moq.dll. You need to add this assembly to your test project in Visual Studio. You also need to add the Moq namespace to your test classes.

What Can Be Mocked?

You can use Moq to create mocks from both interfaces and existing classes. There are some requirements on the classes. The class can’t be sealed. Furthermore, the method being mocked must be marked as virtual. You cannot mock static methods (use the adaptor pattern to mock a static method).
These limitations are the same as the limitations you face when working with Rhino Mocks. Both Moq and Rhino Mocks use proxy classes under the covers. Indeed, both frameworks derive from the same Castle DynamicProxy code base.

Mocking Methods and Properties

Imagine that you are building a database-driven web application. Imagine, for example, that you are creating an online store. You want to concentrate on writing all of the business logic for your store before doing anything else. In particular, you don’t want to devote any time to writing your data access components before writing your business components.
This is a good situation to take advantage of a Mock Object Framework. In this situation, you can create an interface that describes how you want your data access component to look. Then, you can simply mock the interface and take advantage of the mock while testing your business logic. The mock enables you to avoid writing code until you are really ready to do it.