In Eclipse+Android, what is the difference between a Project and a "Test Project"?

I copied th开发者_如何学Goe ApiDemos sample to my workspace, then tried creating a new project out of it. The New Android Project wizard page is obvious but then the wizard led me to a page named "New Android Test Project", which creates a new "Android Test Project resource".

What is that "test resource" and where I can learn more about it?

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A test project allows you to test your app using JUnit; it's not too complete as one would expect but works fine. Take a look at this article: Hello, Testing. There are projects which also allow you to test your Android apps, and which have more features. For instance, take a look at the Robolectric project.