Akka.Streams.Tests.Dsl.RestartSpec.A_restart_with_backoff_flow_should_not_restart_on_completion_when_maxRestarts_is_reached: racy specs

[Aaronontheweb]

One of the raciest tests in the suite currently

Assertion failure:

System.Exception : [ExpectNextN] expected 2 next elements but received 1 elements before an exception occured. Received: [out complete]
---- Failed: Timeout 00:00:03 while waiting for a message of type Akka.Streams.TestKit.TestSubscriber+OnNext`1[System.String] 

Stack trace

   at Akka.Streams.TestKit.TestSubscriber.ManualProbe`1.ExpectNextNTask(TestProbe probe, Int64 n, Nullable`1 timeout, CancellationToken cancellationToken)+MoveNext() in /home/vsts/work/1/s/src/core/Akka.Streams.TestKit/TestSubscriber_Shared.cs:line 214
   at Akka.Streams.TestKit.TestSubscriber.ManualProbe`1.ExpectNextNTask(TestProbe probe, Int64 n, Nullable`1 timeout, CancellationToken cancellationToken)+System.Threading.Tasks.Sources.IValueTaskSource<System.Boolean>.GetResult()
   at System.Linq.AsyncEnumerable.<ToListAsync>g__Core|424_0[TSource](IAsyncEnumerable`1 source, CancellationToken cancellationToken) in /_/Ix.NET/Source/System.Linq.Async/System/Linq/Operators/ToList.cs:line 36
   at System.Linq.AsyncEnumerable.<ToListAsync>g__Core|424_0[TSource](IAsyncEnumerable`1 source, CancellationToken cancellationToken) in /_/Ix.NET/Source/System.Linq.Async/System/Linq/Operators/ToList.cs:line 36
   at Akka.Streams.Tests.Dsl.RestartSpec.<A_restart_with_backoff_flow_should_not_restart_on_completion_when_maxRestarts_is_reached>b__40_0() in /home/vsts/work/1/s/src/core/Akka.Streams.Tests/Dsl/RestartSpec.cs:line 1025
   at Akka.Streams.TestKit.Utils.<>c__DisplayClass5_0.<<AssertAllStagesStoppedAsync>b__0>d.MoveNext() in /home/vsts/work/1/s/src/core/Akka.Streams.TestKit/Utils.cs:line 59
--- End of stack trace from previous location ---
   at Akka.TestKit.Extensions.TaskExtensions.<>c__DisplayClass5_0`1.<<ShouldCompleteWithin>b__0>d.MoveNext()
--- End of stack trace from previous location ---
   at FluentAssertions.Specialized.GenericAsyncFunctionAssertions`1.CompleteWithinAsync(TimeSpan timeSpan, String because, Object[] becauseArgs)
   at Akka.TestKit.Extensions.TaskExtensions.ShouldCompleteWithin[T](Task`1 task, TimeSpan timeout, String because, Object[] becauseArgs)
   at Akka.Streams.TestKit.Utils.AssertAllStagesStoppedAsync[T](TestKitBase spec, Func`1 block, IMaterializer materializer, Nullable`1 timeout, CancellationToken cancellationToken)
   at Akka.Streams.TestKit.Utils.AssertAllStagesStoppedAsync(TestKitBase spec, Func`1 block, IMaterializer materializer, Nullable`1 timeout, CancellationToken cancellationToken) in /home/vsts/work/1/s/src/core/Akka.Streams.TestKit/Utils.cs:line 57
   at Akka.Streams.Tests.Dsl.RestartSpec.A_restart_with_backoff_flow_should_not_restart_on_completion_when_maxRestarts_is_reached() in /home/vsts/work/1/s/src/core/Akka.Streams.Tests/Dsl/RestartSpec.cs:line 1016
--- End of stack trace from previous location ---
----- Inner Stack Trace -----
   at Akka.TestKit.Xunit2.XunitAssertions.Fail(String format, Object[] args) in /home/vsts/work/1/s/src/contrib/testkits/Akka.TestKit.Xunit2/XunitAssertions.cs:line 26
   at Akka.TestKit.TestKitBase.InternalExpectMsgEnvelopeAsync[T](Nullable`1 timeout, Action`2 assert, String hint, CancellationToken cancellationToken, Boolean shouldLog) in /home/vsts/work/1/s/src/core/Akka.TestKit/TestKitBase_Expect.cs:line 436
   at Akka.TestKit.TestKitBase.InternalExpectMsgEnvelopeAsync[T](Nullable`1 timeout, Action`1 msgAssert, Action`1 senderAssert, String hint, CancellationToken cancellationToken) in /home/vsts/work/1/s/src/core/Akka.TestKit/TestKitBase_Expect.cs:line 411
   at Akka.TestKit.TestKitBase.InternalExpectMsgAsync[T](Nullable`1 timeout, Action`1 msgAssert, Action`1 senderAssert, String hint, CancellationToken cancellationToken) in /home/vsts/work/1/s/src/core/Akka.TestKit/TestKitBase_Expect.cs:line 379
   at Akka.Streams.TestKit.TestSubscriber.ManualProbe`1.ExpectNextNTask(TestProbe probe, Int64 n, Nullable`1 timeout, CancellationToken cancellationToken)+MoveNext()