// Initialize stream manager (using is required to destroy cosmos local directory after test)
// You can also consider to create this object once for test class.
// 
using (VirtualStreamManager streamManager = new VirtualStreamManager())
{
    VC.Override.Attach(streamManager);

    try
    {
        // Run tested method here, like
        // 
        MyClass.CreateReportSteams();

        // Manipulate streams
        // 
        streamManager.Delete("/my/stream");

        // Run other tested method
        // 
        MyClass.VerifyReportStreamsExist();

        ...
    }
    finally
    {
        VC.Override.Clear();
    }

    Assert.AreEqual(0, streamManager.OpenedStreams.Count);
}