Running junit tests in parallel in a Maven build?

StackOverflow https://stackoverflow.com/questions/423627

  •  05-07-2019
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Question

I'm using JUnit 4.4 and Maven and I have a large number of long-running integration tests.

When it comes to parallelizing test suites there are a few solutions that allow me to run each test method in a single test-class in parallel. But all of these require that I change the tests in one way or another.

I really think it would be a much cleaner solution to run X different test classes in X threads in parallel. I have hundreds of tests so I don't really care about threading individual test-classes.

Is there any way to do this?

Was it helpful?

Solution 2

From junit 4.7 it's now possible to run tests in parallel without using TestNG. Actually it has been possible since 4.6, but there are a number of fixes being made in 4.7 that will make it a viable option. You may also run parallel tests with spring, which you can read about here

OTHER TIPS

Use maven plugin:

<build>
    <plugins>
    <plugin>
        <groupId>org.apache.maven.plugins</groupId>
        <artifactId>maven-surefire-plugin</artifactId>
        <version>2.7.1</version>
        <configuration>
            <parallel>classes</parallel>
            <threadCount>5</threadCount>
        </configuration>
    </plugin>
    </plugins>
</build>

Inspired by JUnit's experimental ParallelComputer runner I've built my own ParallelSuite and ParallelParameterized runners. Using these runners one can easily parallelize test suites and parameterized tests.

ParallelSuite.java

public class ParallelSuite extends Suite {

    public ParallelSuite(Class<?> klass, RunnerBuilder builder) throws InitializationError {

        super(klass, builder);

        setScheduler(new RunnerScheduler() {

            private final ExecutorService service = Executors.newFixedThreadPool(4);

            public void schedule(Runnable childStatement) {
                service.submit(childStatement);
            }

            public void finished() {
                try {
                    service.shutdown();
                    service.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
                } catch (InterruptedException e) {
                    e.printStackTrace(System.err);
                }
            }
        });
    }
}

ParallelParameterized.java

public class ParallelParameterized extends Parameterized {

    public ParallelParameterized(Class<?> arg0) throws Throwable {

        super(arg0);

        setScheduler(new RunnerScheduler() {

            private final ExecutorService service = Executors.newFixedThreadPool(8);

            public void schedule(Runnable childStatement) {
                service.submit(childStatement);
            }

            public void finished() {
                try {
                    service.shutdown();
                    service.awaitTermination(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
                } catch (InterruptedException e) {
                    e.printStackTrace(System.err);
                }
            }
        });
    }
}

Usage is simple. Just change @RunWith annotations value to one of these Parallel* classes.

@RunWith(ParallelSuite.class)
@SuiteClasses({ATest.class, BTest.class, CTest.class})
public class ABCSuite {}

tempus-fugit offers something similar, check the docs for details. It relies on JUnit 4.7 and you just mark your test to @RunWith(ConcurrentTestRunner).

Cheers

TestNG can do that (this was my first reflex - then I saw you're already having a lot of testcases).

For JUnit, look at parallel-junit.

You can check out the open source library - Test Load Balancer. It does exactly what you ask for - run different test classes in parallel. This integrates at the ant-junit level so that you do not have to change your tests in anyway. I am one of the authors of the library.

Also, think about not running them in threads as you may need a process level sandbox. For example, if you are hitting a DB in your integration tests, you do not want one test to fail because another test added some data in a different thread. Most of the times, tests are not written with this in mind.

Finally, how have solved this problem till now?

You can run the tests in parallel using ParallelComputer provided by Junit itself. Here's a small snippet to get you started.

Class[] cls = { TestCase1.class, TestCase2.class };
Result result = JUnitCore.runClasses(ParallelComputer.classes(), cls);
List<Failure> failures = result.getFailures();

This will help when you need to run tests from code as it has no dependencies on Maven or any other build management tools.

Please note that, this will run all test cases in parallel, if you have any dependencies between different test cases it might result in false positives. You SHOULD NOT have interdependent tests anyway.

You can change your test to be TestNg test in a minute (you just need to change imports), TestNG is the best in parallel testing.

You could try Gridgain that lets you run distribute your tests across a compute grid.

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