[jira] [Created] (SUREFIRE-1169) JUnit / Arquillian lifecycle friendly test execution with forkCount > 1 and reusableForks = true

["Falko Modler (JIRA)" <ji...@apache.org>]

Falko Modler created SUREFIRE-1169:
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             Summary: JUnit / Arquillian lifecycle friendly test execution with forkCount > 1 and reusableForks = true
                 Key: SUREFIRE-1169
                 URL: https://issues.apache.org/jira/browse/SUREFIRE-1169
             Project: Maven Surefire
          Issue Type: Improvement
          Components: process forking
    Affects Versions: 2.18.1
            Reporter: Falko Modler


The current approach to "stream" each test class name to a fork via {{TestProvidingInputStream}} yields a good "load balancing" accross the forks but it *triggers the entire test lifecycle for each test*.

With {{forkCount = 1}}, all tests are executed in one set but with {{forkCount = n}} (n > 1) each test is a separate "set" (so to say).
This is very problematic in case you or a test framwork you are using relies on a certain lifecycle.
[Arquillian|http://arquillian.org/] for example ties various "events" to JUnit's lifecycle methods, like {{AfterSuite}} to {{RunListener.testRunFinished(...)}} which triggers the shutdown of the managed server etc.

When using multiple forks, {{RunListener.testRunFinished(...)}} is called for *every* single test class, triggering {{AfterSuite}} for every single test, although the fork will receive further tests after that which should "reuse" the server.
This is just an example. In fact the whole JUnit / Arquillian lifecycle is inconsistent when using multiple forks.

>From a user perspective I wouldn't expect this behaviour:
As {{forkCount = 1}} (and {{reusableForks = true}}) triggers {{RunListener.testRunFinished(...)}} *once*, {{forkCount = n}} (and {{reusableForks = true}}) should trigger that method *n* times, not *x* times.
To be fair, the [documentation|https://maven.apache.org/surefire/maven-surefire-plugin/examples/fork-options-and-parallel-execution.html] *does* contain a pointer to that problem by saying:
{quote}
When using reuseForks=true and a forkCount value larger than one, test classes are handed over to the forked process one-by-one.
{quote}
But the consequences remain very unclear.

*(Possible) Solution:*

I took a stab at this and implemented an "eager test distribution" to the forks in {{ForkStart.java}} and disabled streaming. Please see attached patch (to be applied against project root, 2.18.1).
Patch Details:
- New config property: {{ForkConfiguration.forksExecuteTestsOneByOne}}, set via Mojo (default is true for backward compatibility, name is debatable)
- When {{forksExecuteTestsOneByOne}} ist set to false, the {{messageQueue}} in {{ForkStarter.runSuitesForkOnceMultiple(...)}} is *not* wrapped in fork specific {{TestProvidingInputStream}} instances to be consumed bit by bit later on.
Instead, the queue is consumed directly and each test class name is assigned to the respective fork by creating a copy of the {{providerProperties}} which is filled individually for each fork.
E.g. for three forks and eight tests:
-- fork 1 executes test 1, 4 and 7
-- fork 2 executes test 2, 5 and 8
-- fork 3 executes test 3 and 6
- To have a clean {{providerProperties}} template I had to move {{DefaultScanResult.writeTo(...)}} to the respective private methods. Otherwise the properties would have contained *all* tests already.
- I refactored some methods in {{ForkStarter}} to enhance readability and to reduce code duplication.
- The patch does *not* contain a test for the new behaviour but all existing tests passed.

{{forksExecuteTestsOneByOne = false}} now leads to a consistent lifecycle.
This solution has one downside: One or more forks could be overloaded while other forks could "underloaded" because you cannot say how long each test will take. runOrder=balanced could help here but has yet to be implemented for forks.




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