Categories in JUnit 4.8

This is from the tests for the upcoming JUnit 4.8 release.  It's the simplest-to-implement framework we could find for labelling tests with named categories, and running only tests with a given label.

 public interface SlowTests extends CategoryType {

 }

 public static class A {
  @Test
  public void a() {
   fail();
  }

  @Category(SlowTests.class)
  @Test
  public void b() {
  }
 }

 @Category(SlowTests.class)
 public static class B {
  @Test
  public void c() {

  }
 }

 public static class C {
  @Test
  public void d() {
   fail();
  }
 }

 @RunWith(Categories.class)
 @IncludeCategory(SlowTests.class)
 @SuiteClasses( { A.class, B.class, C.class })
 public static class SlowTestSuite {
 }