As a workaround, if you are happy with all your tests using the same timeout, you can set it in the constructor (an @Before method does not work)

public class WithTimeoutTest {

    @Rule
    public JenkinsRule jenkinsRule = new JenkinsRule();

    public WithTimeoutTest()
    {
        jenkinsRule.timeout=1;
    }

    // @WithTimeout(1)
    @Test
    public void testFailsAfter1Second() throws InterruptedException {
        Thread.sleep(181_000);
    }
}

Hi Steve,

Well in our case neither works. With the approach suggested by you, the print in the log shows the changed value, however the test is still aborted in 3 mins. 
Test timed out (after 1500 seconds).

@WithTimeout is not supported. JenkinsRule uses the timeout mechanism internally. You should only use the timeout field.

As requested on the dev list, please specify the version of jenkins-test-harness you are using.

jenkins-test-harness version 2.31

It's not supported?

https://github.com/jenkinsci/jenkins-test-harness/blob/master/src/main/java/org/jvnet/hudson/test/recipes/WithTimeout.java#L67

Sorry, I thought you were talking about JUnit’s Timeout rule. Yeah @WithTimeout ought to work if it is there. I do not recall ever using it though, and it is not tested, so perhaps it got broken at some point, most likely 2.25.