TypeAsserter

A micro-framework for unit testing class and type declarations.

###Why?

TDD traditionally tests code functionality. But what about expected types? For example, often times an API is exposed through public interfaces while hiding the implementation with an internal class. TypeAsserter allows you to easily create tests for the expected types of your classes to help protect against modifying the type in unexpected ways.

###Usage

Simply add TypeAsserter to your Unit Test project through the Visual Studio Nuget Package Manager and import the TypeAsserter namespace. Alternatively, clone the GitHub repository. Once the TypeAsserter assembly is added to your Unit Test project, you can then use the available static methods from the AssertClass<T> class.

###Examples

Let's say you have an internal class named MyFoo that is sealed and implements the IFoo interface:

// example class with interface
internal sealed class MyFoo : IFoo { }

// Unit Tests verifying the MyFoo type
[TestClass]
public class MyTests
{
    [TestMethod]
    public void MyFoo_TypeDeclarations()
    {
        AssertClass<MyFoo>.IsInternal();
        AssertClass<MyFoo>.IsSealed();
        AssertClass<MyFoo>.ImplementsInterface<IFoo>();
    }
    
    [TestMethod]
    [ExpectedException( typeof( AssertFailedException ) )]
    public void MyFoo_IsStatic_Fails()
    {
        // Here we are ensuring MyFoo is not static
        AssertClass.IsStatic( typeof( MyFoo ), ClassVisibility.Internal );
    }
}

###Methods

The method names should be self-explanatory. The following is a partial list of available methods that are most commonly used:

AssertClass<T>.IsInternal();
AssertClass<T>.IsPublic();
AssertClass<T>.IsAbstract();
AssertClass<T>.IsNotAbstract();
AssertClass<T>.IsSealed();
AssertClass<T>.IsNotSealed();
AssertClass<T>.InheritsBaseClass<TBaseClass>();
AssertClass<T>.InheritsAbstractBaseClass<TAbstractClass>();
AssertClass<T>.ImplementsInterface<TInterface>();

// static classes cannot be used as generic constraints so you must pass in the
// type to the IsStatic method, i.e., typeof( MyFoo )
AssertClass.IsStatic( Type type, ClassVisibility visibility );