JUnit 3 apparently doesn't like this change, it doesn't find the test cases anymore if they are not directly extending junit.framework.TestCase. This leads for all tests to the exception:

junit.framework.AssertionFailedError: No tests found in org.eclipse.egit.core.T0003_AdaptableFileTreeIteratorTest
	at junit.framework.Assert.fail(Assert.java:47)
	at junit.framework.TestSuite$1.runTest(TestSuite.java:90)
...