I try to be as specific and useful as possible in my questions here at SO, but for that, well, it means almost nothing, because I have absolutely no hint of how this happens.
This happens on any / every test (even "empty"). And I already tried (uninstalling and) updating unity. - Does not work.
In any case, here is the exception stop code:
2017.11.16 14:54:24.308 ERROR System.Reflection.TargetInvocationException: Uma exceção foi acionada pelo destino de uma chamada.
System.Reflection.TargetInvocationException: Uma exceção foi acionada pelo destino de uma chamada. ---> System.InvalidCastException: Não é possível converter um objeto do tipo 'NUnit.Engine.CallbackHandler' no tipo 'System.Web.UI.ICallbackEventHandler'.
em NUnit.Framework.Api.FrameworkController.LoadTestsAction..ctor(FrameworkController controller, Object handler)
--- Fim do rastreamento de pilha de exceções internas ---
em System.RuntimeMethodHandle._InvokeConstructor(Object[] args, SignatureStruct& signature, IntPtr declaringType)
em System.Reflection.RuntimeConstructorInfo.Invoke(BindingFlags invokeAttr, Binder binder, Object[] parameters, CultureInfo culture)
em System.RuntimeType.CreateInstanceImpl(BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes)
em System.Activator.CreateInstance(String assemblyName, String typeName, Boolean ignoreCase, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes, Evidence securityInfo, StackCrawlMark& stackMark)
em System.Activator.CreateInstance(String assemblyName, String typeName, Boolean ignoreCase, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes, Evidence securityInfo)
em System.AppDomain.CreateInstance(String assemblyName, String typeName, Boolean ignoreCase, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes, Evidence securityAttributes)
em System.AppDomain.CreateInstanceAndUnwrap(String assemblyName, String typeName, Boolean ignoreCase, BindingFlags bindingAttr, Binder binder, Object[] args, CultureInfo culture, Object[] activationAttributes, Evidence securityAttributes)
em NUnit.Engine.Drivers.NUnit3FrameworkDriver.Load(String testAssemblyPath, IDictionary`2 settings)
em NUnit.Engine.Runners.DirectTestRunner.LoadPackage()
em NUnit.Engine.Runners.AbstractTestRunner.Load()
em NUnit.Engine.Runners.MasterTestRunner.LoadPackage()
em NUnit.Engine.Runners.AbstractTestRunner.EnsurePackageIsLoaded()
em NUnit.Engine.Runners.MasterTestRunner.NUnit.Engine.ITestRunner.Explore(TestFilter filter)
em JetBrains.ReSharper.UnitTestRunner.nUnit30.BuiltInNUnitRunner.<>c__DisplayClass1.<RunTests>b__0()
em JetBrains.ReSharper.UnitTestRunner.nUnit30.BuiltInNUnitRunner.WithExtensiveErrorHandling(IRemoteTaskServer server, Action action)
This has been giving me quite a bit of code without (unit-) testing over the past few days, so if anyone has an idea of the cause and / or solutions, it will be very helpful.