Unit test doesn't return forever

When i run the unit tests for my current project, one of the tests seems to be in an endless loop. It doesn't return, even if i try to cancel the unit test run. I have to close Rider or kill the unit test runner process. When i run the same test with the Visual Studio test runner, it returns after a few seconds. When i use the Resharper test runner in Visual Studio, the test runs also endless.

I'm using Version 2020.3 of Rider (and Resharper). The unit tests are implemented with MsTest. The log has the following content (i have made it anonymous):

08:43:00.787 |T| Launch: e691b6f8-9db3-4a83-b59e-87a42edee8f8 >> UnityTaskRunnerHostController.AfterLaunchStarted
08:43:00.787 |T| Launch: e691b6f8-9db3-4a83-b59e-87a42edee8f8 << UnityTaskRunnerHostController.AfterLaunchStarted
08:43:00.788 |I| BuildStage started
08:43:00.788 |I| Build policy: Automatic
08:43:01.675 |I| 0 projects built
08:43:01.675 |V|
08:43:01.675 |I| BuildStage completed
08:43:01.675 |I| RefreshProjectPropertiesStage started
08:43:01.675 |I| RefreshProjectPropertiesStage completed
08:43:01.675 |I| DiscoveryStage started
08:43:01.676 |I| Test exploration required for 0 projects
08:43:01.676 |V|
08:43:01.676 |I| DiscoveryStage completed
08:43:01.676 |I| BuildPipelineStage started
08:43:01.676 |I| BuildPipelineStage completed
08:43:01.676 |I| ApplyRulesStage started
08:43:01.677 |V| Running elements from criterion: {ConjunctiveCriterion: {TestAncestorCriterion: MSTest::4864B84E-F49D-4510-9AB2-3EA913486976::.NETFramework,Version=v4.7.2::<<MyTestClass.MyTestMethod>>}, {TestAncestorCriterion: MSTest::4864B84E-F49D-4510-9AB2-3EA913486976::.NETFramework,Version=v4.7.2::<<MyTestClass.MyTestMethod>>}}
08:43:01.677 |I| Got 1 elements (1 explicit) to run
08:43:01.677 |V| Marking 1 elements as Pending
08:43:01.678 |V| Marking elements as Pending completed
08:43:01.678 |V| Distributing 1 elements into runs
08:43:01.678 |V| Distributing elements completed
08:43:01.678 |I| Created 1 unit-test runs
08:43:01.678 |I| ApplyRulesStage completed
08:43:01.678 |I| RunTestsStage started
08:43:01.678 |I| Running up to 4 unit-test runs in parallel
08:43:01.678 |I| Run: 7ccfd354-3a96-48d3-b52b-ec06b920699c - Starting
08:43:01.678 |V| Provider: MSTest
Target Framework: .NETFramework,Version=v4.7.2
Strategy: MsTestTestRunnerRunStrategy
Runtime Environment: TestRunnerRuntimeEnvironment
Project: <<MyUnitTestProject>>
TargetPlatform: X64
TargetFrameworkId: .NETFramework,Version=v4.7.2
RunAsTargetFrameworkId: .NETFramework,Version=v4.7.2
IsUnmanaged: False
08:43:01.678 |T| Run: 7ccfd354-3a96-48d3-b52b-ec06b920699c >> UnityTaskRunnerHostController.PrepareForRun
08:43:01.678 |T| Run: 7ccfd354-3a96-48d3-b52b-ec06b920699c << UnityTaskRunnerHostController.PrepareForRun
08:43:01.693 |V| [ProcessStartInfoPatchResult]
Original request: FrameworkRequest (UseInternal: False, UseMono: False, MonoDebugMode: True, MonoPlatform: PreferX64)
Success: True
ErrorMessage: <Empty>
Original StartInfo: FileName = '<<UserFolder>>\AppData\Local\JetBrains\Installations\Rider203_000\lib\ReSharperHost\TestRunner\net461\ReSharperTestRunner64.exe', Arguments = '-f .NETFramework,Version=v4.7.2 -p 55421 -r 7ccfd354-3a96-48d3-b52b-ec06b920699c --parentProcessId 14656', WorkDir = <<MyWorkingDir>>'
Patched StartInfo: FileName = '<<UserFolder>>\AppData\Local\JetBrains\Installations\Rider203_000\lib\ReSharperHost\TestRunner\net461\ReSharperTestRunner64.exe', Arguments = '-f .NETFramework,Version=v4.7.2 -p 55421 -r 7ccfd354-3a96-48d3-b52b-ec06b920699c --parentProcessId 14656', WorkDir = <<MyWorkingDir>>'

08:43:01.693 |I| Starting process: <<UserFolder>>\AppData\Local\JetBrains\Installations\Rider203_000\lib\ReSharperHost\TestRunner\net461\ReSharperTestRunner64.exe -f .NETFramework,Version=v4.7.2 -p 55421 -r 7ccfd354-3a96-48d3-b52b-ec06b920699c --parentProcessId 14656
08:43:01.697 |I| Started process with pid 15692
08:43:02.565 |V| TestRunner: Application Installed ServerLogTarget
08:43:02.576 |V| TestRunner: ClientEndpoint Message handler 'JetBrains.ReSharper.TestRunner.Implementation.UnitTestRemoteAgent' registered for message type 'JetBrains.ReSharper.TestRunner.Abstractions.Objects.RemoteAgentInitializationRequest'
08:43:02.592 |V| TestRunner: ClientEndpoint Message handler 'JetBrains.ReSharper.TestRunner.Implementation.UnitTestRemoteAgent' registered for message type 'JetBrains.ReSharper.TestRunner.Abstractions.Objects.TestRunRequest'
08:43:02.592 |V| TestRunner: ClientEndpoint Message handler 'JetBrains.ReSharper.TestRunner.Implementation.UnitTestRemoteAgent' registered for message type 'JetBrains.ReSharper.TestRunner.Abstractions.Objects.TestDiscoveryRequest'
08:43:02.592 |V| TestRunner: ClientEndpoint Message handler 'JetBrains.ReSharper.TestRunner.Implementation.UnitTestRemoteAgent' registered for message type 'JetBrains.ReSharper.TestRunner.Abstractions.Objects.RequestAbortMessage'
08:43:02.609 |V| RunSettings:
<RunSettings><RunConfiguration><ResultsDirectory><<MySolutionDir>>\TestResults</ResultsDirectory><SolutionDirectory><<MySolutionDir>></SolutionDirectory><TargetPlatform>X64</TargetPlatform><TargetFrameworkVersion>.NETFramework,Version=v4.7.2</TargetFrameworkVersion></RunConfiguration></RunSettings>
08:43:02.620 |V| TestRunner: TestAdapterLoadContextFactoryFactory Registered protocol entities: 8 scalars and 0 serializers
08:43:02.628 |V| TestRunner: DefaultTestAdapterLoadContextFactory Initializing test adapter load context: NoIsolation = False
08:43:02.643 |I| TestRunner: ShadowCopyBehavior+NoShadowCopyBehavior Shadow-copy will be skipped as it is disabled
08:43:02.691 |V| TestRunner: AssemblyLoader(Tests) AssemblyLoader installed into Tests
08:43:02.691 |V| TestRunner: AssemblyLoader(Tests) Tests: Added probing path '<<UserFolder>>\AppData\Local\JetBrains\Installations\Rider203_000\lib\ReSharperHost\TestRunner\net461'
08:43:02.707 |V| TestRunner: TestAdapterLoadContext Using application configuration: <<MyConfigFile>>
08:43:02.707 |V| TestRunner: AssemblyLoader(Tests) Tests: Assembly 'JetBrains.ReSharper.TestRunner.Abstractions, Version=1.2.7.0, Culture=neutral, PublicKeyToken=5c492ec4f3eccde3' resolved from '<<UserFolder>>\AppData\Local\JetBrains\Installations\Rider203_000\lib\ReSharperHost\TestRunner\net461\JetBrains.ReSharper.TestRunner.Abstractions.dll'
08:43:02.707 |V| TestRunner: LoadContextTracker Load context Tests is non-collectible and will not be tracked
08:43:02.721 |V| TestRunner: AssemblyLoader(Tests) Tests: Added probing path '<<UserFolder>>\AppData\Local\JetBrains\Installations\Rider203_000\lib\ReSharperHost\TestRunner\Adapters\MsTest\net451'
08:43:02.721 |V| TestRunner: AssemblyLoader(Tests) Tests: Added probing path <<MyWorkingDir>>'
08:43:02.737 |V| TestRunner: AssemblyLoader(Tests) Tests: Assembly 'JetBrains.ReSharper.TestRunner.Core, Version=1.2.7.47, Culture=neutral, PublicKeyToken=5c492ec4f3eccde3' resolved from '<<UserFolder>>\AppData\Local\JetBrains\Installations\Rider203_000\lib\ReSharperHost\TestRunner\net461\JetBrains.ReSharper.TestRunner.Core.dll'
08:43:02.753 |V| TestRunner: TestAdapterLoadContextWrapper Initialized test executor: JetBrains.ReSharper.TestRunner.Adapters.MsTest.MsTestRunner, JetBrains.ReSharper.TestRunner.Adapters.MsTest, Version=1.2.7.21, Culture=neutral, PublicKeyToken=5c492ec4f3eccde3
08:43:02.753 |V| TestRunner: AssemblyLoader(Tests) Tests: Assembly 'JetBrains.ReSharper.TestRunner.Adapters.MsTest.Tasks, Version=1.2.7.7, Culture=neutral, PublicKeyToken=5c492ec4f3eccde3' resolved from '<<UserFolder>>\AppData\Local\JetBrains\Installations\Rider203_000\lib\ReSharperHost\TestRunner\Adapters\MsTest\net451\JetBrains.ReSharper.TestRunner.Adapters.MsTest.Tasks.dll'
08:43:02.753 |I| TestRunner: MsTestRunner Execution started
08:43:02.800 |V| TestRunner: MsTestRunner AssemblyLoader installed into MSTest Tests
08:43:02.800 |V| TestRunner: MsTestRunner MSTest Tests: Added probing path '<<UserFolder>>\AppData\Local\JetBrains\Installations\Rider203_000\lib\ReSharperHost\TestRunner\Adapters\MsTest\net451'
08:43:02.800 |V| TestRunner: MsTestRunner MSTest Tests: Added probing path '<<UserFolder>>\AppData\Local\JetBrains\Installations\Rider203_000\lib\ReSharperHost\TestRunner\net461'
08:43:02.816 |V| TestRunner: MsTestRunner MSTest Tests: Assembly 'JetBrains.ReSharper.TestRunner.Abstractions, Version=1.2.7.0, Culture=neutral, PublicKeyToken=5c492ec4f3eccde3' resolved from '<<UserFolder>>\AppData\Local\JetBrains\Installations\Rider203_000\lib\ReSharperHost\TestRunner\net461\JetBrains.ReSharper.TestRunner.Abstractions.dll'
08:43:02.816 |V| TestRunner: MsTestRunner MSTest Tests: Added probing path <<MyWorkingDir>>'
08:43:02.846 |V| TestRunner: AssemblyLoader(Tests) Tests: Assembly 'JetBrains.ReSharper.TestRunner.Adapters.MsTest, Version=1.2.7.21, Culture=neutral, PublicKeyToken=5c492ec4f3eccde3' resolved from '<<UserFolder>>\AppData\Local\JetBrains\Installations\Rider203_000\lib\ReSharperHost\TestRunner\Adapters\MsTest\net451\JetBrains.ReSharper.TestRunner.Adapters.MsTest.dll'
08:43:02.862 |V| TestRunner: MsTestRunner MSTest Tests: Assembly 'Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter' resolved from <<MyWorkingDir>>\Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.dll'
08:43:02.862 |V| TestRunner: MsTestRunner MSTest Tests: Assembly 'JetBrains.Lifetimes, Version=777.0.0.0, Culture=neutral, PublicKeyToken=3c74c1a6a8683340' resolved from '<<UserFolder>>\AppData\Local\JetBrains\Installations\Rider203_000\lib\ReSharperHost\TestRunner\net461\JetBrains.Lifetimes.dll'
08:43:02.940 |V| TestRunner: MsTestRunner MSTest Tests: Assembly 'Microsoft.TestPlatform.Utilities, Version=15.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' not resolved
08:43:03.347 |V| TestRunner: MsTestRunner MSTest Tests: Assembly 'Microsoft.VisualStudio.TestPlatform.Extensions.MSAppContainerAdapter' not resolved
08:43:03.347 |V| TestRunner: MsTestRunner MSTest Tests: Assembly 'Microsoft.VisualStudio.TestTools.CppUnitTestFramework.CppUnitTestExtension' not resolved
08:43:03.378 |V| TestRunner: MsTestRunner MSTest Tests: Assembly 'Microsoft.VisualStudio.TestPlatform.Common.resources, Version=15.0.0.0, Culture=de-DE, PublicKeyToken=b03f5f7f11d50a3a' not resolved
08:43:03.565 |V| TestRunner: MsTestRunner MSTest Tests: Assembly 'Microsoft.VisualStudio.TestPlatform.MSTestAdapter.PlatformServices, Version=14.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' resolved from <<MyWorkingDir>>\Microsoft.VisualStudio.TestPlatform.MSTestAdapter.PlatformServices.dll'
08:43:03.613 |V| TestRunner: MsTestRunner MSTest Tests: Assembly 'Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter, Version=14.0.0.0, Culture=neutral, PublicKeyToken=b03f5f7f11d50a3a' resolved from <<MyWorkingDir>>\Microsoft.VisualStudio.TestPlatform.MSTest.TestAdapter.dll'
08:43:03.722 |V| TestRunner: MsTestRunner MSTest Tests: Assembly 'Microsoft.VisualStudio.TestPlatform.ObjectModel.resources, Version=15.0.0.0, Culture=de-DE, PublicKeyToken=b03f5f7f11d50a3a' not resolved
08:43:03.762 |V| Run: 7ccfd354-3a96-48d3-b52b-ec06b920699c - Discovery result processing started
08:43:03.763 |V| Run: 7ccfd354-3a96-48d3-b52b-ec06b920699c - Discovery result processing finished (+0 -0 ~0)
08:43:03.768 |V| TestRunner: Discoverer Sending discovery results to server...
08:43:03.893 |V| TestRunner: MsTestRunner MSTest Tests: Assembly 'Microsoft.VisualStudio.TestPlatform.MSTestAdapter.PlatformServices.resources, Version=14.0.0.0, Culture=de-DE, PublicKeyToken=b03f5f7f11d50a3a' not resolved
08:46:50.311 |I| Run: 7ccfd354-3a96-48d3-b52b-ec06b920699c - is being cancelled
08:47:10.140 |I| Process <<UserFolder>>\AppData\Local\JetBrains\Installations\Rider203_000\lib\ReSharperHost\TestRunner\net461\ReSharperTestRunner64.exe:15692 has exited with code (1)
08:47:10.147 |E| Process <<UserFolder>>\AppData\Local\JetBrains\Installations\Rider203_000\lib\ReSharperHost\TestRunner\net461\ReSharperTestRunner64.exe:15692 exited with code '1'.

--- EXCEPTION #1/1 [LoggerException]
Message = “Process <<UserFolder>>\AppData\Local\JetBrains\Installations\Rider203_000\lib\ReSharperHost\TestRunner\net461\ReSharperTestRunner64.exe:15692 exited with code '1'.”
ExceptionPath = Root
ClassName = JetBrains.Util.LoggerException
HResult = COR_E_APPLICATION=80131600
StackTraceString = “
bei JetBrains.ReSharper.UnitTestFramework.TestRunner.TestRunnerRunStrategy.OnExit(IPreparedProcess runner, Int32 exitCode, ITestRunnerExecutionContext ctx)
bei JetBrains.ReSharper.UnitTestFramework.TestRunner.TestRunnerRunStrategy.Run(IUnitTestRun run)
bei JetBrains.ReSharper.UnitTestFramework.Launch.UnitTestRun.<StartCore>d__33.MoveNext()
bei System.Runtime.CompilerServices.AsyncTaskMethodBuilder.Start[TStateMachine](TStateMachine& stateMachine)
bei JetBrains.ReSharper.UnitTestFramework.Launch.UnitTestRun.StartCore(CancellationToken onCancel, CancellationToken onAbort)
bei JetBrains.ReSharper.UnitTestFramework.Launch.UnitTestRun.<Start>d__32.MoveNext()
bei System.Runtime.CompilerServices.AsyncTaskMethodBuilder.Start[TStateMachine](TStateMachine& stateMachine)
bei JetBrains.ReSharper.UnitTestFramework.Launch.UnitTestRun.Start(CancellationToken onCancel, CancellationToken onAbort)
bei System.Threading.Tasks.Task`1.InnerInvoke()
bei System.Threading.Tasks.Task.Execute()
bei System.Threading.ExecutionContext.RunInternal(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
bei System.Threading.ExecutionContext.Run(ExecutionContext executionContext, ContextCallback callback, Object state, Boolean preserveSyncCtx)
bei System.Threading.Tasks.Task.ExecuteWithThreadLocal(Task& currentTaskSlot)
bei System.Threading.Tasks.Task.ExecuteEntry(Boolean bPreventDoubleExecution)
bei System.Threading.ThreadPoolWorkQueue.Dispatch()
”

08:47:10.147 |T| Run: 7ccfd354-3a96-48d3-b52b-ec06b920699c >> UnityTaskRunnerHostController.CleanupAfterRun
08:47:10.147 |T| Run: 7ccfd354-3a96-48d3-b52b-ec06b920699c << UnityTaskRunnerHostController.CleanupAfterRun
08:47:10.148 |I| Run: 7ccfd354-3a96-48d3-b52b-ec06b920699c - Cancelled
08:47:10.148 |I| RunTestsStage completed
08:47:10.148 |I| FinishLaunchStage started
08:47:10.149 |I| Finishing launch
08:47:10.149 |I| Launch is finished
08:47:10.149 |I| FinishLaunchStage completed
08:47:10.149 |T| Launch: e691b6f8-9db3-4a83-b59e-87a42edee8f8 >> UnityTaskRunnerHostController.BeforeLaunchFinished
08:47:10.149 |T| Launch: e691b6f8-9db3-4a83-b59e-87a42edee8f8 << UnityTaskRunnerHostController.BeforeLaunchFinished