JUnit4TestAdapter blocks JUnit-3-style suites that are included via @RunWith(Suite.class)

[mkeller]

The intention of junit.framework.JUnit4TestAdapter is to allow a JUnit-3-style test runner to run JUnit-4-style tests.

However, due to a bug in JUnit, this doesn't work when a JUnit-4-style test suite (@RunWith(Suite.class)) includes a JUnit-3-style suite class.
Happened to us in https://bugs.eclipse.org/bugs/show_bug.cgi?id=474777

To reproduce in JUnit itself:

• remove the @RunWith(AllTests.class) annotation from org.junit.tests.junit3compatibility.OldTests
• run the whole org.junit.tests.AllTests:
  • if you run it with a JUnit-4-style runner, it passes
  • but with a JUnit-3-style runner that calls the suite() method, it fails with:

AllTests (org.junit.tests)
org.junit.tests.AllTests
org.junit.tests.junit3compatibility.OldTests
initializationError(org.junit.tests.junit3compatibility.OldTests)
java.lang.Exception: No runnable methods
    at org.junit.runners.BlockJUnit4ClassRunner.validateInstanceMethods(BlockJUnit4ClassRunner.java:202)
    at org.junit.runners.BlockJUnit4ClassRunner.collectInitializationErrors(BlockJUnit4ClassRunner.java:138)
    at org.junit.runners.ParentRunner.validate(ParentRunner.java:416)
    at org.junit.runners.ParentRunner.<init>(ParentRunner.java:84)
    at org.junit.runners.BlockJUnit4ClassRunner.<init>(BlockJUnit4ClassRunner.java:68)
    at org.junit.internal.builders.JUnit4Builder.runnerForClass(JUnit4Builder.java:10)
    at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:59)
    at org.junit.internal.builders.AllDefaultPossibilitiesBuilder.runnerForClass(AllDefaultPossibilitiesBuilder.java:26)
    at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:59)
    at org.junit.runners.model.RunnerBuilder.runners(RunnerBuilder.java:101)
    at org.junit.runners.model.RunnerBuilder.runners(RunnerBuilder.java:87)
    at org.junit.runners.Suite.<init>(Suite.java:102)
    at org.junit.runners.Suite.<init>(Suite.java:70)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
    at sun.reflect.NativeConstructorAccessorImpl.newInstance(NativeConstructorAccessorImpl.java:39)
    at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(DelegatingConstructorAccessorImpl.java:27)
    at java.lang.reflect.Constructor.newInstance(Constructor.java:501)
    at org.junit.internal.builders.AnnotatedBuilder.buildRunner(AnnotatedBuilder.java:108)
    at org.junit.internal.builders.AnnotatedBuilder.runnerForClass(AnnotatedBuilder.java:86)
    at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:59)
    at org.junit.internal.builders.AllDefaultPossibilitiesBuilder.runnerForClass(AllDefaultPossibilitiesBuilder.java:26)
    at org.junit.runners.model.RunnerBuilder.safeRunnerForClass(RunnerBuilder.java:59)
    at org.junit.internal.requests.ClassRequest.getRunner(ClassRequest.java:33)
    at junit.framework.JUnit4TestAdapter.<init>(JUnit4TestAdapter.java:40)
    at junit.framework.JUnit4TestAdapter.<init>(JUnit4TestAdapter.java:34)
    at org.junit.tests.AllTests.suite(AllTests.java:246)
...

I'm preparing a pull request.