Parallel test configuration in JUnit - Test Execution Trace

Test Overview

This test demonstrates how to configure and run tests in parallel using JUnit 5. It verifies that two simple tests run concurrently without interfering with each other.

Test Code - JUnit 5

JUnit

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.parallel.Execution;
import org.junit.jupiter.api.parallel.ExecutionMode;
import static org.junit.jupiter.api.Assertions.assertTrue;

@Execution(ExecutionMode.CONCURRENT)
public class ParallelTest {

    @Test
    void testOne() throws InterruptedException {
        Thread.sleep(500); // Simulate work
        assertTrue(true);
    }

    @Test
    void testTwo() throws InterruptedException {
        Thread.sleep(500); // Simulate work
        assertTrue(true);
    }
}

Execution Trace - 5 Steps

Step	Action	System State	Assertion	Result
1	JUnit test runner starts and detects tests annotated with @Execution(CONCURRENT)	Test runner is ready to run tests in parallel	-	PASS
2	Test runner launches testOne and testTwo simultaneously on separate threads	Both tests are running concurrently	-	PASS
3	testOne executes Thread.sleep(500) then asserts true	testOne is running and simulating work	assertTrue(true) passes	PASS
4	testTwo executes Thread.sleep(500) then asserts true	testTwo is running and simulating work	assertTrue(true) passes	PASS
5	Both tests complete successfully without interference	Test runner collects results	Both tests passed	PASS

Failure Scenario

Failing Condition: If tests are not configured to run in parallel or share mutable state causing interference

Execution Trace Quiz - 3 Questions

What annotation enables parallel execution of tests in JUnit 5?

A @ParallelTest

B @RunWith(ParallelRunner.class)

C @Execution(ExecutionMode.CONCURRENT)

D @ConcurrentExecution

Key Result

Use @Execution(ExecutionMode.CONCURRENT) to run JUnit 5 tests in parallel safely, and avoid shared mutable state to prevent flaky tests.