[Xcode 11] RegisterFontDescriptors_WithCallback from FontManagerTest fails in Beta 5

[dalexsoto]

The following monotouch-test is getting disabled for beta 5 since it started randomingly failing

https://github.com/xamarin/xamarin-macios/blob/9bcedc65bf5c329e095a350c368b04abef1bcdd9/tests/monotouch-test/CoreText/FontManagerTest.cs#L220-L238

[FAIL] FontManagerTest.RegisterFontDescriptors_WithCallback :   errors
  Expected: 0
  But was:  1

		  at MonoTouchFixtures.CoreText.FontManagerTest.SuccessDone (Foundation.NSError[] errors, System.Boolean done) [0x00001] in /Users/builder/jenkins/workspace/xamarin-macios-pr-builder/tests/monotouch-test/CoreText/FontManagerTest.cs:123 
		  at CoreText.CTFontManager.TrampolineRegistrationHandler (System.IntPtr block, System.IntPtr errors, System.Boolean done) [0x00007] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.99.2.30/src/Xamarin.iOS/CoreText/CTFontManager.cs:162 
		  at (wrapper native-to-managed) CoreText.CTFontManager.TrampolineRegistrationHandler(intptr,intptr,int)
		  at (wrapper managed-to-native) CoreText.CTFontManager.CTFontManagerRegisterFontDescriptors(intptr,CoreText.CTFontManagerScope,bool,ObjCRuntime.BlockLiteral&)
		  at CoreText.CTFontManager.RegisterFontDescriptors (CoreText.CTFontDescriptor[] fontDescriptors, CoreText.CTFontManagerScope scope, System.Boolean enabled, CoreText.CTFontManager+CTFontRegistrationHandler registrationHandler) [0x0003a] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.99.2.30/src/Xamarin.iOS/CoreText/CTFontManager.cs:374 
		  at MonoTouchFixtures.CoreText.FontManagerTest.RegisterFontDescriptors_WithCallback () [0x0004d] in /Users/builder/jenkins/workspace/xamarin-macios-pr-builder/tests/monotouch-test/CoreText/FontManagerTest.cs:232 
		  at (wrapper managed-to-native) System.Reflection.RuntimeMethodInfo.InternalInvoke(System.Reflection.RuntimeMethodInfo,object,object[],System.Exception&)
		  at System.Reflection.RuntimeMethodInfo.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x0006a] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.99.2.30/src/Xamarin.iOS/mcs/class/corlib/System.Reflection/RuntimeMethodInfo.cs:391 
		--- End of stack trace from previous location where exception was thrown ---
		  at (wrapper managed-to-native) CoreText.CTFontManager.CTFontManagerRegisterFontDescriptors(intptr,CoreText.CTFontManagerScope,bool,ObjCRuntime.BlockLiteral&)
		  at CoreText.CTFontManager.RegisterFontDescriptors (CoreText.CTFontDescriptor[] fontDescriptors, CoreText.CTFontManagerScope scope, System.Boolean enabled, CoreText.CTFontManager+CTFontRegistrationHandler registrationHandler) [0x0003a] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.99.2.30/src/Xamarin.iOS/CoreText/CTFontManager.cs:374 
		  at MonoTouchFixtures.CoreText.FontManagerTest.RegisterFontDescriptors_WithCallback () [0x0004d] in /Users/builder/jenkins/workspace/xamarin-macios-pr-builder/tests/monotouch-test/CoreText/FontManagerTest.cs:232 
		  at (wrapper managed-to-native) System.Reflection.RuntimeMethodInfo.InternalInvoke(System.Reflection.RuntimeMethodInfo,object,object[],System.Exception&)
		  at System.Reflection.RuntimeMethodInfo.Invoke (System.Object obj, System.Reflection.BindingFlags invokeAttr, System.Reflection.Binder binder, System.Object[] parameters, System.Globalization.CultureInfo culture) [0x0006a] in /Library/Frameworks/Xamarin.iOS.framework/Versions/12.99.2.30/src/Xamarin.iOS/mcs/class/corlib/System.Reflection/RuntimeMethodInfo.cs:391 

[VincentDondain]

Still failing on iOS beta 7, disabling the test, let's get at GM

[VincentDondain]

Ignored here: #6833

[rolfbjarne]

I tried looking at the test to see if it needed to be fixed, but no matter what I did (and I tried a lot of things) I couldn't make it work. Then again the documentation is still scarce, so it might be that we're using the API incorrectly.

We should probably try again with stable, and also check if there is better documentation or even working code samples online.