JUnit test for an expected timeout

Question

I have a test of communication over a TCP socket where I expect the server to not respond within a set time frame when I send a certain message.

The servers behaviour is nothing I can control.

I know how to fail a test if it has not completed within a set time frame. But how can I do the opposite, make it pass for not completing within the timeframe?

I can use @Test (timeout=1000) to make a test fail if not complete within a second.

But, using Junit 4, is there a function to test for an expected timeout as a positive result? I.e. The test will fail if completed within the time frame and pass if not?

Answer 1

Good question. Actually you can do this using only junit tools. My idea is to inverse Timeout rule behaviour + use expected attribute of Test annotation. The only one limitation: you have to place your test in separate class, because Rule applies to all tests inside it:

public class Q37355035 {

    private static final int MIN_TIMEOUT = 100;

    @Rule
    public Timeout timeout = new Timeout(MIN_TIMEOUT) {
        public Statement apply(Statement base, Description description) {
            return new FailOnTimeout(base, MIN_TIMEOUT) {
                @Override
                public void evaluate() throws Throwable {
                    try {
                        super.evaluate();
                        throw new TimeoutException();
                    } catch (Exception e) {}
                }
            };
        }
    };

    @Test(expected = TimeoutException.class)
    public void givesTimeout() throws InterruptedException {
        TimeUnit.SECONDS.sleep(1);
    }
}