nunit: InternalTrace.Initialize fails with Nullref exception

When testing the 4.3.1 NUnit3Testadapter I’m experiencing crashes in the InternalTrace.Initialize, which raises a nullref exception.

The stacktrace and messages are

SendMessage: Current directory: D:\repos\NUnit\nunit3-vs-adapter\src\NUnitTestAdapterTests\bin\Debug\netcoreapp3.1
SendMessage:    Exception thrown executing tests in D:\repos\NUnit\nunit3-vs-adapter\src\NUnitTestAdapterTests\bin\Debug\netcoreapp3.1\mock-assembly.dll
SendMessage: NUnit.Engine.NUnitEngineException: An exception occurred in the driver while loading tests.
 ---> System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation.
 ---> System.NullReferenceException: Object reference not set to an instance of an object.
   at NUnit.Framework.Internal.InternalTrace.Initialize(String logName, InternalTraceLevel level)
   at NUnit.Framework.Api.FrameworkController.Initialize(String assemblyNameOrPath, IDictionary settings)
   at NUnit.Framework.Api.FrameworkController..ctor(String assemblyNameOrPath, String idPrefix, IDictionary settings)
   at NUnit.Framework.Api.FrameworkController..ctor(Assembly assembly, String idPrefix, IDictionary settings)
   --- End of inner exception stack trace ---
   at System.RuntimeMethodHandle.InvokeMethod(Object target, Object[] arguments, Signature sig, Boolean constructor, Boolean wrapExceptions)
   at System.Reflection.RuntimeConstructorInfo.Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
   at System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture)
   at System.Activator.CreateInstance(Type type, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)
   at System.Activator.CreateInstance(Type type, Object[] args)
   at NUnit.Engine.Drivers.NUnitNetStandardDriver.CreateObject(String typeName, Object[] args)
   at NUnit.Engine.Drivers.NUnitNetStandardDriver.Load(String testAssembly, IDictionary`2 settings)
   at NUnit.Engine.Runners.DirectTestRunner.LoadDriver(IFrameworkDriver driver, String testFile, TestPackage subPackage)
   --- End of inner exception stack trace ---
   at NUnit.Engine.Runners.DirectTestRunner.LoadDriver(IFrameworkDriver driver, String testFile, TestPackage subPackage)
   at NUnit.Engine.Runners.DirectTestRunner.LoadPackage()
   at NUnit.Engine.Runners.DirectTestRunner.EnsurePackageIsLoaded()
   at NUnit.Engine.Runners.DirectTestRunner.Explore(TestFilter filter)
   at NUnit.Engine.Runners.MasterTestRunner.Explore(TestFilter filter)
   at NUnit.VisualStudio.TestAdapter.NUnitEngine.NUnitEngineAdapter.Explore(TestFilter filter) in d:\repos\NUnit\nunit3-vs-adapter\src\NUnitTestAdapter\NUnitEngine\NUnitEngineAdapter.cs:line 98
   at NUnit.VisualStudio.TestAdapter.NUnit3TestExecutor.RunAssembly(String assemblyPath, IGrouping`2 testCases, TestFilter filter) in d:\repos\NUnit\nunit3-vs-adapter\src\NUnitTestAdapter\NUnit3TestExecutor.cs:line 286
SendMessage:    at NUnit.Engine.Runners.DirectTestRunner.LoadDriver(IFrameworkDriver driver, String testFile, TestPackage subPackage)
   at NUnit.Engine.Runners.DirectTestRunner.LoadPackage()
   at NUnit.Engine.Runners.DirectTestRunner.EnsurePackageIsLoaded()
   at NUnit.Engine.Runners.DirectTestRunner.Explore(TestFilter filter)
   at NUnit.Engine.Runners.MasterTestRunner.Explore(TestFilter filter)
   at NUnit.VisualStudio.TestAdapter.NUnitEngine.NUnitEngineAdapter.Explore(TestFilter filter) in d:\repos\NUnit\nunit3-vs-adapter\src\NUnitTestAdapter\NUnitEngine\NUnitEngineAdapter.cs:line 98
   at NUnit.VisualStudio.TestAdapter.NUnit3TestExecutor.RunAssembly(String assemblyPath, IGrouping`2 testCases, TestFilter filter) in d:\repos\NUnit\nunit3-vs-adapter\src\NUnitTestAdapter\NUnit3TestExecutor.cs:line 286
SendMessage: NUnit Adapter 4.3.1.0: Test execution complete

This does not happen during normal runs, but when running some of the tests in the adapter,

The code for this {in the adapter repo] is currently in the Fixtmppath branch.

Looking at the NUnit code for the InternalTrace.Initialize method, I can’t see that much that can go wrong, but line https://github.com/nunit/nunit/blob/92180f13381621e308b01f0abd1a397cc1350c12/src/NUnitFramework/framework/Internal/Logging/InternalTrace.cs#L54 could raise this. The property Initialized is actually a check for the traceWriter != null, but as these are independent they could [theoretically] deviate. I might be missing something here, but anyway, it crashes in this method.