What does a erlenmeyer flask icon over project in visual studio mean?

Question

I've searched high and low, but cannot find out what this icon indicates. It appears over one of my project icons in visual studio (2012). See image below:

Thanks in advance for any help.

Answer 1

It says that the particular project is a Test case project.

Answer 2

I don't think it's a SourceGear Vault icon. Vault only shows icons for source control status, like checked out, old, renegade, etc.

It might be a beaker, and an icon in Visual Studio. See this from Microsoft:

http://connect.microsoft.com/VisualStudio/feedback/details/774775/test-project-icon-toggles-when-expanding-collapsing