Allow parallel test runs with SBT

[SimY4]

Testing Problem

Getting this error quite frequently. Not sure why. Running tests from SBT, nothing was updated recently except SBT itself.

Test com.github.simy4.coregex.jqwik.CoregexArbitraryProviderTest.shouldGenerateAnyString failed: java.util.ConcurrentModificationException: null, took 0.044s
[error]     at java.util.HashMap.computeIfAbsent(HashMap.java:1221)
[error]     at net.jqwik.engine.execution.lifecycle.StoreRepository.addStore(StoreRepository.java:56)
[error]     at net.jqwik.engine.execution.lifecycle.StoreRepository.create(StoreRepository.java:51)
[error]     at net.jqwik.engine.facades.StoreFacadeImpl.create(StoreFacadeImpl.java:19)
[error]     at net.jqwik.api.lifecycle.Store.create(Store.java:67)
[error]     at net.jqwik.engine.hooks.statistics.StatisticsHook.aroundProperty(StatisticsHook.java:31)
[error]     at net.jqwik.engine.execution.lifecycle.HookSupport.lambda$wrap$1(HookSupport.java:31)
[error]     at net.jqwik.engine.execution.lifecycle.HookSupport.lambda$wrap$0(HookSupport.java:26)
[error]     at net.jqwik.engine.hooks.lifecycle.AutoCloseableHook.aroundProperty(AutoCloseableHook.java:13)
[error]     at net.jqwik.engine.execution.lifecycle.HookSupport.lambda$wrap$1(HookSupport.java:31)
[error]     at net.jqwik.engine.execution.PropertyMethodExecutor.execute(PropertyMethodExecutor.java:47)
[error]     at net.jqwik.engine.execution.PropertyTaskCreator.executeTestMethod(PropertyTaskCreator.java:166)
[error]     at net.jqwik.engine.execution.PropertyTaskCreator.lambda$createTask$1(PropertyTaskCreator.java:51)
[error]     at net.jqwik.engine.execution.lifecycle.CurrentDomainContext.runWithContext(CurrentDomainContext.java:28)
[error]     at net.jqwik.engine.execution.PropertyTaskCreator.lambda$createTask$2(PropertyTaskCreator.java:50)
[error]     at net.jqwik.engine.execution.pipeline.ExecutionTask$1.lambda$execute$0(ExecutionTask.java:31)
[error]     at net.jqwik.engine.execution.lifecycle.CurrentTestDescriptor.runWithDescriptor(CurrentTestDescriptor.java:17)
[error]     at net.jqwik.engine.execution.pipeline.ExecutionTask$1.execute(ExecutionTask.java:31)
[error]     at net.jqwik.engine.execution.pipeline.ExecutionPipeline.runToTermination(ExecutionPipeline.java:82)
[error]     at net.jqwik.engine.execution.JqwikExecutor.execute(JqwikExecutor.java:46)
[error]     at net.jqwik.engine.JqwikTestEngine.executeTests(JqwikTestEngine.java:70)
[error]     at net.jqwik.engine.JqwikTestEngine.execute(JqwikTestEngine.java:53)

[SimY4]

It started happening after I introduced some tests using jqwik-testing. Removing tests removes the issue. 🤷

[jlink]

Latest version of jqwik?

[jlink]

One more question: Does it happen in the context of concurrent code or is everything in the tests running in a single thread?

[SimY4]

@jlink latwst released. 1.7.4

I'm not sure how SBT runs unit tests, I need to check. Instead of CME, sometimes it's becomes ArrayIndexOutOfBoundException in the same class. Something there is not ready to deal with what SBT is doing. I'll run some more experiments today.

[jlink]

I deployed a pathetically simple attempt to fix the problem on "1.8.0-SNAPSHOT". @SimY4 Maybe you'll find the time to try it.

[jlink]

@SimY4 You could also try with disabling parallel tests in SBT as described here.

[SimY4]

Let me check. This is ArrayIndexOutOfBoundsException BTW for completeness:

java.lang.ArrayIndexOutOfBoundsException: Index 3 out of bounds for length 3, took 0.156s
[error]     at java.util.LinkedHashMap.valuesToArray(LinkedHashMap.java:555)
[error]     at java.util.LinkedHashMap$LinkedValues.toArray(LinkedHashMap.java:635)
[error]     at java.util.ArrayList.<init>(ArrayList.java:181)
[error]     at net.jqwik.engine.execution.lifecycle.StoreRepository.streamAllStores(StoreRepository.java:127)
[error]     at net.jqwik.engine.execution.lifecycle.StoreRepository.finishScope(StoreRepository.java:107)
[error]     at net.jqwik.engine.execution.ContainerTaskCreator.lambda$createTask$3(ContainerTaskCreator.java:91)
[error]     at net.jqwik.engine.execution.pipeline.ExecutionTask$1.lambda$execute$0(ExecutionTask.java:31)
[error]     at net.jqwik.engine.execution.lifecycle.CurrentTestDescriptor.runWithDescriptor(CurrentTestDescriptor.java:17)
[error]     at net.jqwik.engine.execution.pipeline.ExecutionTask$1.execute(ExecutionTask.java:31)
[error]     at net.jqwik.engine.execution.pipeline.ExecutionPipeline.runToTermination(ExecutionPipeline.java:82)
[error]     at net.jqwik.engine.execution.JqwikExecutor.execute(JqwikExecutor.java:46)
[error]     at net.jqwik.engine.JqwikTestEngine.executeTests(JqwikTestEngine.java:70)
[error]     at net.jqwik.engine.JqwikTestEngine.execute(JqwikTestEngine.java:53)

[SimY4]

@jlink can confirm that Test / parallelExecution := false fixes this issue in SBT.

[jlink]

@jlink can confirm that Test / parallelExecution := false fixes this issue in SBT.

Then my fix has at least a chance of working. Try 1.8.0-SNAPSHOT.

[SimY4]

On latest snapshot I'm getting this most of the time (arbitrary in question varies from every run):

Test com.github.simy4.coregex.jqwik.JqwikTest.arbitraryTest failed: net.jqwik.api.CannotFindArbitraryException: Cannot find an Arbitrary for Parameter of type [@net.jqwik.api.ForAll(value="", supplier=net.jqwik.api.ArbitrarySupplier$NONE.class) Random], took 0.128s
[error]     at net.jqwik.engine.properties.RandomizedShrinkablesGenerator.resolveArbitraries(RandomizedShrinkablesGenerator.java:152)
[error]     at net.jqwik.engine.properties.RandomizedShrinkablesGenerator.resolveEdgeCases(RandomizedShrinkablesGenerator.java:124)
[error]     at net.jqwik.engine.properties.RandomizedShrinkablesGenerator.listOfEdgeCases(RandomizedShrinkablesGenerator.java:93)
[error]     at net.jqwik.engine.properties.RandomizedShrinkablesGenerator.forParameters(RandomizedShrinkablesGenerator.java:28)
[error]     at net.jqwik.engine.execution.CheckedProperty.createRandomizedShrinkablesGenerator(CheckedProperty.java:236)
[error]     at net.jqwik.engine.execution.CheckedProperty.createForAllParametersGenerator(CheckedProperty.java:176)
[error]     at net.jqwik.engine.execution.CheckedProperty.createGenericProperty(CheckedProperty.java:144)
[error]     at net.jqwik.engine.execution.CheckedProperty.check(CheckedProperty.java:67)
[error]     at net.jqwik.engine.execution.PropertyMethodExecutor.executeProperty(PropertyMethodExecutor.java:90)
[error]     at net.jqwik.engine.execution.PropertyMethodExecutor.executeMethod(PropertyMethodExecutor.java:69)
[error]     at net.jqwik.engine.execution.PropertyMethodExecutor.lambda$execute$0(PropertyMethodExecutor.java:49)
[error]     at net.jqwik.api.lifecycle.AroundPropertyHook.lambda$static$0(AroundPropertyHook.java:46)
[error]     at net.jqwik.engine.execution.lifecycle.HookSupport.lambda$wrap$0(HookSupport.java:26)
[error]     at net.jqwik.api.lifecycle.PropertyExecutor.executeAndFinally(PropertyExecutor.java:39)
[error]     at net.jqwik.engine.hooks.lifecycle.PropertyLifecycleMethodsHook.aroundProperty(PropertyLifecycleMethodsHook.java:56)
[error]     at net.jqwik.engine.execution.lifecycle.HookSupport.lambda$wrap$1(HookSupport.java:31)
[error]     at net.jqwik.engine.execution.lifecycle.HookSupport.lambda$wrap$0(HookSupport.java:26)
[error]     at net.jqwik.engine.hooks.statistics.StatisticsHook.aroundProperty(StatisticsHook.java:37)
[error]     at net.jqwik.engine.execution.lifecycle.HookSupport.lambda$wrap$1(HookSupport.java:31)
[error]     at net.jqwik.engine.execution.lifecycle.HookSupport.lambda$wrap$0(HookSupport.java:26)
[error]     at net.jqwik.engine.hooks.lifecycle.AutoCloseableHook.aroundProperty(AutoCloseableHook.java:13)
[error]     at net.jqwik.engine.execution.lifecycle.HookSupport.lambda$wrap$1(HookSupport.java:31)
[error]     at net.jqwik.engine.execution.PropertyMethodExecutor.execute(PropertyMethodExecutor.java:47)
[error]     at net.jqwik.engine.execution.PropertyTaskCreator.executeTestMethod(PropertyTaskCreator.java:166)
[error]     at net.jqwik.engine.execution.PropertyTaskCreator.lambda$createTask$1(PropertyTaskCreator.java:51)
[error]     at net.jqwik.engine.execution.lifecycle.CurrentDomainContext.runWithContext(CurrentDomainContext.java:28)
[error]     at net.jqwik.engine.execution.PropertyTaskCreator.lambda$createTask$2(PropertyTaskCreator.java:50)
[error]     at net.jqwik.engine.execution.pipeline.ExecutionTask$1.lambda$execute$0(ExecutionTask.java:31)
[error]     at net.jqwik.engine.execution.lifecycle.CurrentTestDescriptor.runWithDescriptor(CurrentTestDescriptor.java:17)
[error]     at net.jqwik.engine.execution.pipeline.ExecutionTask$1.execute(ExecutionTask.java:31)
[error]     at net.jqwik.engine.execution.pipeline.ExecutionPipeline.runToTermination(ExecutionPipeline.java:82)
[error]     at net.jqwik.engine.execution.JqwikExecutor.execute(JqwikExecutor.java:46)
[error]     at net.jqwik.engine.JqwikTestEngine.executeTests(JqwikTestEngine.java:70)
[error]     at net.jqwik.engine.JqwikTestEngine.execute(JqwikTestEngine.java:53)

Some other things I observed less frequently:

• ArrayIndexOutOfBounds
• StreamCorruptionException during deserialization of .jqwik-database

[jlink]

That all suggests that SBT test parallelisation does things that are not compatible with the way jqwik currently works. I don’t know how fine-grained it can be switched off (eg for jqwik only) and if this has severe performance penalties for your build, though.

[jlink]

@SimY4 To dive deeper and to enable this kind of parallelisation I'd need a test field for exploring SBT parallelisation. If you find the time to provide a minimum project using SBT running several jqwik tests, I'll look into the underlying problems. Not now, but when 1.8.0 will be done and deployed.

[jlink]

Assumption: SBT is using several instances of the test engine concurrently. Probably via several launcher instances or starting launches in parallel threads.

Potential Problems

• Access to singletons like StoreRepostiory are not prepared for that
• ThreadLocals may not work as expected
• Generator caching may not work
• Serialization and Deserialization of jqwik database cannot cope
• Lifecycle may get confused

[SimY4]

@jlink I reproduced it on this project: https://github.com/SimY4/coregex

Steps to reproduce:

• remove Test / parallelExecution := false from jqwik project
• run the build pipeline or for the faster dev loop:

sh> sbt
> project jqwik
> test

[jlink]

@SimY4 Many thanks