Parallelize test execution in a @Rule

Question

I want to reuse some integration tests for load testing purposes. I implemented a rule which is parameterized by an annotation:

@Target(ElementType.METHOD)
@Retention(RetentionPolicy.RUNTIME)
public @interface Parallel {

    int invocations() default 1;

    int rampUpTime() default 0;
}

In my rule implementation the annotation is evaluated and a statement is set up, which has a evaluate method like that:

@Override
public void evaluate() throws Throwable {
    ScheduledExecutorService exe = Executors.newScheduledThreadPool(invocations);

    for (int i = 0; i < invocations; i++) {
        ScheduledFuture<?> scheduledFuture = exe.schedule(new Runnable() {

            @Override
            public void run() {
                try {
                    invocated++;

                    // Request test = Request.method(description.getTestClass(), description.getMethodName());
                    // new JUnitCore().run(test);

                    statement.evaluate();
                } catch (Throwable e) {
                    e.printStackTrace();
                }
            }
        }, i * rampUpTime, this.timeUnit);
        futures.add(scheduledFuture);
    }
}

So, the evaluate call gets wrapped in a Runnable() and scheduled as described in the annotation. The thing is: In my rule, only the scheduling takes place, the runner doesn´t know (or care) about all the runables which only run as long as it takes to set up the whole test suite. So I´m trying to add the calls to evalute() to the test runner. First try was to use JUnitCore.run(...) which of course ends in a recursion.

Next try was to collect all the futures and wait for them to finish. This works fine on a per test basis, but I want to execute a whole test suite in parallel. And also, in my test report, I only see the test being executed once.

So then I thought I use a parameterized suite with a context (an object which collects all the futures from all tests) as parameter, but I didn´t found a way to promote this context object to the tests, each test has to have its own parameters.

I´m now asking for a way to add multiple executions from my rule to the test runner which is executing it.

Answer 1

If I'm understanding you correctly, you are trying to control the execution behaviour of the test runner. A TestRule might be to limited to achieve that goal. But how about writing your own Runner which controls the execution flow of your unit test? Just have a look at the ParentRunner of JUnit. From there, you should get a pretty good idea how the basic scheduling works, and maybe implement your own version of org.junit.experimental.ParallelComputer.