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Is it possible to tell Maven2 to execute every jUnit test in new JVM instance (fork) in serial mode, i.e. one by one.
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Once parallel test execution property is enabled, the JUnit Jupiter engine will execute tests in parallel according to the provided configuration with declared synchronization mechanisms.
Maven Dependencies In a nutshell, Surefire provides two ways of executing tests in parallel: Multithreading inside a single JVM process. Forking multiple JVM processes.
By enabling parallel execution, the JUnit engine starts using the ForkJoin thread pool. Next, we need to add a configuration to utilize this thread pool. We need to choose a parallelization strategy. JUnit provides two implementations (dynamic and fixed) and a custom option to create our implementation.
The surefire offers a variety of options to execute tests in parallel, allowing you to make best use of the hardware at your disposal. But forking in particular can also help keeping the memory requirements low.
You have to fork the JVM like explained here
<plugin>
<groupId>org.apache.maven.plugins</groupId>
<artifactId>maven-surefire-plugin</artifactId>
<version>2.9</version>
<configuration>
<forkMode>always</forkMode>
</configuration>
</plugin>
It should also be possible by just declaring a Sytem property
mvn -DforkMode=always test
As described in the documentation: "always" forks for each test-class. I do not know if the "pertest" setting will fork for each test.
Thanks to @Djebel for pointing out that forkMode is deprecated now. There is a detailed documentation on "Fork Options and Parallel Test Execution" and how to use the new parameters forkCount and reuseForks and that also includes the following migration tips:
Old Setting New Setting
forkMode=once (default) forkCount=1 (default), reuseForks=true (default)
forkMode=always forkCount=1 (default), reuseForks=false
forkMode=never forkCount=0
forkMode=perthread, threadCount=N forkCount=N, (reuseForks=false, if you did not had that one set)
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