I recently noticed a bit of a problem when playing with threads within JUnit. Take the following snippet as an example;

@Test
public void exaple() {
    Thread thread = new Thread(new Runnable() {
        @Override
        public void run() {
            System.out.println("hello");
            try {
                Thread.sleep(10000);
            } catch (InterruptedException e) {
                Thread.interrupt();
            }
            System.out.println("bye");
        }
    });
    assertThat(thread.isDaemon(), is(NON_DAEMON));
    thread.start();
}

Here, the string “bye” is never shown, it would seem that when the test method finishes it somehow messes with the threads…

Looking into things, it seems in my case that naughty Eclipse is muddying the water! The RemoteTestRunner class which Eclipse uses to run the tests ends up calling System.exit(0) after it’s run all the tests to kill the parent Java process. Even if we changed the daemon status of the thread, you’d get the same behaviour, ie, no “bye” being shown.

So, in some situations it is possible to kill a thread in a JUnit test bypassing the interrupt mechanism when running a test from Eclipse. IntelliJ actually seems to have the same behaviour but I can’t review to source to confirm.