ReSharper unit test runner gives Inconclusive to the outer class

I have unit tests written using nUnit and tests are structured in a similar way as in Phil Haack's post

namespace MyNamespace
{
    [TestFixture]
    public class ClassToTest
    {
        [TestFixture]
        public class MethodToTest
        {
            [Test]
            public void ThrowsArgumentNullException_OnNullIndex()
            {
                ...
            }

            .. more tests for the method ..
        }

        [TestFixture]
        public class AnotherMethodToTest
        {
            [Test]
            public void ThrowsArgumentNullException_OnNullIndex()
            {
                ...
            }

            .. more tests for the method ..
        }
    }
}

My problem is that I get inconclusive for the outer class that is used to group unit tests. I have tried with and without [TestFixture] on the outer and/or inner class, but it is always giving me Inconclusive.

I think the correct behavior should be to display unit test states from the inner class tests. Any ideas?

Update

One ugly fix seems to be creating a dummy test to the outer class and then put attribute Ignore on it.

[Test, Ignore]
public void DummyTest()
{
    Assert.IsTrue(true);
}

Update 2

Channs & Wayne are correct, outer class is just used for grouping, so changing from class to namespace is the best solution.