[BUG] Unit testing .NET Core WPF applications fails with TypeLoadException

[anaisbetts]

Describe the bug

Unit testing .NET Core WPF apps doesn't work because getting MainThreadScheduler blows up even though we're in a test runner.

  Message: 
    System.TypeInitializationException : The type initializer for 'ReactiveUI.RxApp' threw an exception.
    ---- System.TypeLoadException : Could not load type 'System.Reactive.Concurrency.DispatcherScheduler' from assembly 'System.Reactive, Version=4.2.0.0, Culture=neutral, PublicKeyToken=94bc3704cddfc263'.
  Stack Trace: 
    RxApp.get_MainThreadScheduler() line 138
    MainWindowViewModel.ctor(IObservable`1 allAppWindows) line 49
    SmokeTests.MainWindowViewModelShouldBeCreatableInRunner() line 13
    ----- Inner Stack Trace -----
    <>c.<Register>b__0_7()
    WaitForDispatcherScheduler.AttemptToCreateScheduler() line 67
    WaitForDispatcherScheduler.ctor(Func`1 schedulerFactory) line 35
    Registrations.Register(Action`2 registerFunction) line 37
    DependencyResolverMixins.ProcessRegistrationForNamespace(String ns, AssemblyName assemblyName, IMutableDependencyResolver resolver) line 120
    <>c__DisplayClass0_0.<InitializeReactiveUI>b__2(String ns) line 47
    CompatMixins.ForEach[T](IEnumerable`1 this, Action`1 block) line 16
    DependencyResolverMixins.InitializeReactiveUI(IMutableDependencyResolver resolver) line 48
    <.cctor>b__9_0() line 87
    InternalLocator.RegisterResolverCallbackChanged(Action callback) line 120
    Locator.RegisterResolverCallbackChanged(Action callback) line 74
    RxApp.cctor() line 89

[open-collective-bot]

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