Allow test parallelisation when forkMode=always

Both parallel forks, balanced parallel forks and reusable forks are part of the long term plan (which is written on the backside of a napkin I have lying around here somewhere - if I haven't lost it). Unfortunately I will not be implementing this until the overall complexity of the surefire forking logic is reduced to a minimum. This has been an ongoing process since at least version 2.8 and will probably continue for a few more versions after 2.11. If anyone wants to take a shot at this, go ahead. Just be warned the code is still changing quite alot in this section.

This request half-overlaps this issue.

I've been to implement it, it seems to fit well with surefire architecture (changes are in one file only).
I used to system property to configure the number of parallel process, but I think this can be changed easily.

This is a cool patch It needs a few minor modifications; I think the regular "threadCount" parameter should be used, and the forkMode should be "perthread".

It also needs an integration test, you should be able to modify (or make a new project based on)
surefire-integration-tests/src/test/resources/runorder-parallel and a test implementation in XmlReporterRunTimeIT.

(I think you can just modify the existing to accept forkMode as a -D parameter instead of hard-coding)

I will be releasing 2.11.1 soon, but I'll schedule this patch for 2.12 if you fix this stuff.

Ok, will do. Do you have something in mind for 2.12 release date?

"Early next year"

v2 includes:

• integration test with surefire-integration-tests/src/test/resources/runorder-parallel
• forkMode is "perThread"
• use threadCount

Fixed in r1222474, thanks for the patch!

I made some adjustments to the patch, and you may want to look over those.

This is not yet in https://repository.apache.org/content/groups/snapshots/org/apache/maven/plugins/maven-surefire-plugin/2.12-SNAPSHOT/maven-surefire-plugin-2.12-20120119.191905-28.jar by the looks of it as I'm getting:

Execution default-test of goal org.apache.maven.plugins:maven-surefire-plugin:2.12-SNAPSHOT:test failed: Fork mode perThread is not a legal value

Any chance you can deploy a snapshot with this patch in?

Thanks nkeywal, one question if you don't mind. I want surefire to fork X JVMs and then spread the tests across them evenly without re-launching new JVM for every test. Looks like this:

<configuration>
    <forkMode>perthread</forkMode>
    <threadCount>2</threadCount>
</configuration>

runs at most 2 JVMs but still launches new JVM instance for every test. Is it possible to reuse JVMs? Our integration tests are heavy to initialise and their initialisation is statically defined, so to avoid re-initialisation there should be JVM reuse.

Yes, I confirm it will relaunch a new jvm for each test. Kristian's comment above says "reusable forks" are in the roadmap. It's not something we need, so I didn't look at it when I implemented the patch. BTW you can parallelize the tests with forkMode=once, and in this case the jvm is not recreated.

Yes, but forkMode=once will only parallelise tests within same JVM using multiple threads, which will not work for us as our tests are inherently not thread safe. We need "1 thread multiple JVMs" type of parallelisation with JVM reuse. I'll think of some workaround in this case.

Re-using VM's is a planned feature, but someone has to implement it

JUnit test parallelization with forkMode=always is supposed to work now?

On my machine (I use Maven Surefire 2.12), with 'always' tests are not run in parallel (although log messages on the console suggest parallel test execution). When I use 'perthread' as forkMode instead, tests are actually run in parallel.

always is linear, single threaded as before.