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Getting different results on different OSes

See original GitHub issue

Stryker is reporting different results on different OSes.

TL;DR

While testing Stryker I stumbled upon an intriguing issue, Stryker was reporting some non-killed mutants which I didn’t think twice about as it seemed it was working as expected. Then I uploaded the project to a private GitLab server and looked at CI results, one mutant was killed (which didn’t happen on my Windows 10 PC).

The issue

When running on Windows 10 (log-20180928-windows-10.txt) or Ubuntu under Windows 10 (log-20180928-windows-10-linux.txt) all running .Net Core SDK 2.1.402 following mutant is marked as Survived but it shouldn’t survive given the test case (see MutationTesting.zip).

Binary expression mutation on line 6: 'temp < 1000' ==> 'temp > 1000'

While running on Docker (image: microsoft/dotnet:2.1.402-sdk) it is killed as expected (log-20180928-linux-docker.txt).

I was trying to replicate on public GitLab server, but I got this error:

[13:49:31 ERR] An error occurred during the mutationtest run 
System.ArgumentOutOfRangeException: Specified argument was out of the range of valid values.
Parameter name: MaxDegreeOfParallelism
   at System.Threading.Tasks.ParallelOptions.set_MaxDegreeOfParallelism(Int32 value)
   at Stryker.Core.MutationTest.MutationTestProcess.Test()
   at Stryker.Core.StrykerRunner.RunMutationTest(StrykerOptions options)

During my testing I also got both mutants killed on Windows 10, which happened after I deleted my native language folder from SDK installation so I could send a proper (English speaking) report. Cleaning output folders did fix this issue and results got back to “normal”.