Test tip with Maven Surefire

When starting a new Maven module, I strongly encourage everybody to set the unit tests to execute in parallel.

There are a few benefits to this:

• most obviously the unit tests run faster on modern multi-cpu boxes
• it helps to tease out concurrent bugs earlier
• it helps to enforce good unit testing practices; specifically that there should be no side effects between tests and the order of test execution should not matter
• enabling this feature later on in a project is possible, but it is nearly always a pain so start it early and you will get its benefits almost for free

I recently introduced this practice to a new team that I am working with and upon enabling it on a recent module whose unit tests were already in a good state it highlighted a concurrency bug in a third party library that was being pulled in that had not yet been detected. Who would have guessed it? Early detection of problems is awesome.

To enable in Maven just add the following runes to you pom.xml file:

<plugin>
    <groupId>org.apache.maven.plugins</groupId>
    <artifactId>maven-surefire-plugin</artifactId>
    <configuration>
        <parallel>methods</parallel>
        <threadCount>2</threadCount>
    </configuration>
</plugin>