Is defining TestMethod's in test base classes not supported by MsTest?

Question

This question concerns a general unit test technique with a potentially very useful wide range of applicable scenarios. But it is easier to understand with an example to illustr

Answer 1

Using VS 2010 I am not seeing the same behavior as you are. When I copied your 2 classes into a test project and compiled it I got the output:

UTA004: Illegal use of attribute...The TestMethodAttribute can be 
defined only inside a class marked with the TestClass attribute

So I marked EqualsFixutureBase:

[TestClass]
public abstract class EqualsFixtureBase
{
...
}

Now it compiles without warning and when I select run tests for ExampleOfAnEqualsTestFixture it runs Foo and all 5 of the inherited equals tests. Also when I copy the ExampleOfAnEqualsTestFixture and use it for int and run the tests for the solution I see all 5 inherited tests running (and passing) for the example string class and the example int class.

Are you doing something in addition to your example which might be causing your problem?