JUnit 4 Test Timeout

Learn to write JUnit tests with timeout behavior. If a test does not complete execution in a given time limit then its execution will be forcefully stopped and the test will be marked failed.

1. Why tests need to be timedout?

We might need to test for the fail-safe behavior of the application that how the application behaves when the external systems do not respond in the given time.

That’s why it is advisable to use timeout-related tests when we are mocking the external dependencies.

This is also considered JUnit best practice to be followed.

How the timeout is invoked?

As we know that each test is run in a new thread. If the specified timeout elapses before the test completes, its execution is interrupted via Thread.interrupt().

2. JUnit test timeout example

To specify the timeout period of a certain test case, “timeout” attribute is mentioned on the annotation @Test.

Note that the timeout time is specified in milliseconds.

@Test(timeout = 500)
public void testTimeoutOne() throws InterruptedException 
{
	TimeUnit.SECONDS.sleep(1);
}

In the above test, execution will be timed out after 500ms with the below message.

java.lang.Exception: test timed out after 500 milliseconds

2. Timeout Rule for Global Timeouts

Rather than specifying the timeout attributes for all the tests separately, we can define JUnit Rule for all tests in a class.

import java.util.concurrent.TimeUnit;

import org.junit.Rule;
import org.junit.Test;
import org.junit.rules.Timeout;

public class TimeoutTests {
	@Rule
	public Timeout globalTimeout = Timeout.seconds(2);

	@Test 	
	public void testTimeoutOne() throws InterruptedException          //PASS
	{
		TimeUnit.SECONDS.sleep(1);
	}

	@Test 	
	public void testTimeoutTwo() throws InterruptedException		//FAIL
	{
		TimeUnit.SECONDS.sleep(3);
	}
}

In the above example, the first test will PASS while the second test will FAIL.

Happy Learning !!

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