ClassNotFoundException: junit.framework.TestCase cannot be found by org.eclipse.xtext.junit_2.4.3.v201309030823

Question

I'm puzzled by this error:

java.lang.NoClassDefFoundError: junit/framework/TestCase
    at java.lang.ClassLoader.defineClass1(Native Method)
    at java.lang.ClassLoader.defineClass(ClassLoader.java:792)
    at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.defineClass(DefaultClassLoader.java:188)
    at org.eclipse.osgi.baseadaptor.loader.ClasspathManager.defineClassHoldingLock(ClasspathManager.java:638)
...
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.loadClass(RemoteTestRunner.java:693)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.loadClasses(RemoteTestRunner.java:429)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:452)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:683)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:390)
    at org.eclipse.pde.internal.junit.runtime.RemotePluginTestRunner.main(RemotePluginTestRunner.java:62)
    at org.eclipse.pde.internal.junit.runtime.CoreTestApplication.run(CoreTestApplication.java:23)
...
Caused by: java.lang.ClassNotFoundException: junit.framework.TestCase cannot be found by org.eclipse.xtext.junit_2.4.3.v201309030823
    at org.eclipse.osgi.internal.loader.BundleLoader.findClassInternal(BundleLoader.java:501)
    at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:421)
    at org.eclipse.osgi.internal.loader.BundleLoader.findClass(BundleLoader.java:412)
    at org.eclipse.osgi.internal.baseadaptor.DefaultClassLoader.loadClass(DefaultClassLoader.java:107)
    at java.lang.ClassLoader.loadClass(ClassLoader.java:357)
    ... 78 more

The exception happens when I run the tests for my Xtext DSL as plugin tests (i.e. when a new Eclipse platform is started internally). This happens before any of my code is executed.

When I look at the plugin dependencies, I can see that org.junit_4.11.0.v201303080030.jar is on the classpath and I also see /.../workspace/.metadata/.plugins/org.eclipse.pde.core/.external_libraries/org.junit_4.11.0.v201303080030/junit.jar

So OSGis should definitely be able to resolve this dependency.

Does Xtext 2.4.3 work with JUnit 4.11 or do I have to downgrade my Eclipse install to JUnit 4.10?

Answer 1

Two points

First

Check your Project Properties->Java Build Path->Libraries (tab). JUnit should be there although this usually will show up in the build.

Check you Project's Run Configurations->JUnit->Classpath (tab). JUnit should be under User Entries for your project.

Second

Check you have below plugins

org.eclipse.xtext.xbase.junit
org.junit (3.8.2)
org.junit (4.8.2)

[EDIT] This got me on the right track. To fix the error make sure you have org.junit 3.8 in the target platform!

Explanation: The error above means that Eclipse itself couldn't start. It seems that the JUnit runner has a dependency on JUnit 3.8. It won't be used but without it, the whole platform can't be initialized.

You can see whether you have the same problem by looking at the stack trace: Does it contain RemotePluginTestRunner.main?

To fix the error, add the org.junit 3.8 bundle to your target platform.