Tuesday, 5 August 2008

Using Junit 4 to run tests repeatedly

We had a problem with a test that would fail intermittently on continuous integration.
The best way to find the problem was by running the test hundreds of times to see the problem.
We used the code below to easily do this:


@RunWith(MyRunner.class)
public class UnusualAndRareProblemTest {
...
..
.
}

public static class MyRunner extends JUnit4ClassRunner {

public MyRunner(Class klass) throws InitializationError {
super(klass);
}

@Override
public void run(final RunNotifier notifier) {
for(int i=0; i<1000; i++) {
super.run(notifier);
}
}
}



It turns out the class under test was spawning threads and we were getting race/dead-locking conditions due to the way we were trying to retrieve the outcomes from different threads.
PS. We fixed this by re-writing the class so that instead of spawning threads directly it made calls to a 'action factory' that we could mock and avoid multi-threading in the test entirely.

2 comments:

Unknown said...

Have you ever checked out testng?

Simple annotations would make running a test multiple times simpler still...
in groovy you could have a test method like:

@Test (invocationCount=3)
void verifyLoudDogBarker(){
assert false : 'dogbarker not loud'
}

to have instances of the test run in parallel just change the annotation to:
@Test (invocationCount=3, threadPoolSize=3)

Danail Nachev said...

This is TestNG annotations, not JUnit. JUnit doesn't support such repeated execution.

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