When using the TestDriven.NET runner against a target namespace, test classes including nested test classes in the namespace are executed. This pull request implements similar behavior when running the TestDriven.NET runner against a target class.

@TheCloudlessSky identified the bug using the following sample class:

class CalculatorTests
{
    class Adding
    {
        public void computes_the_sum()
        {
            var sut = new Calculator();

            var result = sut.Add(1, 2);

            result.ShouldEqual(3);
        }
    }

    class Subtracting
    {
        public void computes_the_difference()
        {
            var sut = new Calculator();

            var result = sut.Subtract(3, 2);

            result.ShouldEqual(1);
        }
    }
}

This pull request ensures that when invoking TestDriven.NET on CalculatorTests, the inner types Adding and Subtracting are also considered by the applicable conventions, instead of only considering CalculatorTests. Doing so brings Fixie's TestDriven.NET in line with the same behavior in the xUnit TestDriven.NET runner. (Naturally, if the conventions don't consider the nested types to be test classes, they'll be rightly skipped over like any other non-test class.)