Assert.IsAssignableFrom

Assert.IsAssignableFrom succeeds if the object provided may be assigned a value of the expected type.

Assert.IsAssignableFrom( Type expected, object actual );
Assert.IsAssignableFrom( Type expected, object actual, 
                         string message, params object[] parms );
Assert.IsAssignableFrom<T>( object actual );
Assert.IsAssignableFrom<T>( object actual, 
                            string message, params object[] parms );

See also...

* Type Constraints