<p>I have a test project using MbUnit and TestDriven.Net.  </p>

<p>If I right-click on an individual test method and say "Run Tests" the test runs successfully.  Same thing if I click on a file name in the solution explorer.  </p>

<p>However, if I right click and say run tests on the project or the solution, TestDriven.Net reports "0 Passed, 0 Failed, 0 Skipped."</p>

<p>I have other similar projects that work just fine, and yes, the classes are labeled [TestFixture] and the methods are labeled [Test].</p>

You need to add testing attributes for your favorite testing framework.  TestDriven picks up these attributes by reflection in order to know what tests to run.
For example, using NUnit.Framework - each test class needs [TextFixture] and each test method needs [Test]
Here's an
example