[XM] Fix test failures (#119)

* [XM] Fix NSAccessibility binding issue breaking tests

* [XM] Don't run extension tests on OS X that don't have extension support

src/appkit.cs

@@ -22807,7 +22807,7 @@ namespace XamCore.AppKit {
 	[Protocol, BaseType (typeof (NSObject))]
 	public interface NSObjectAccessibilityExtensions {
 		[Availability (Obsoleted = Platform.Mac_10_10, Message = "Use the NSAccessibility protocol methods instead")]
-		[Export ("accessibilityAttributeNames:")]
+		[Export ("accessibilityAttributeNames")]
 		NSArray AccessibilityAttributeNames { get; }
 
 		[Availability (Obsoleted = Platform.Mac_10_10, Message = "Use the NSAccessibility protocol methods instead")]

tests/mmptest/src/ExtensionTests.cs

@@ -15,6 +15,9 @@ namespace Xamarin.MMP.Tests
 		[Test]
 		public void TodayExtension_SmokeTest ()
 		{
+			if (!PlatformHelpers.CheckSystemVersion (10, 10))
+				return;
+
 			RunMMPTest (tmpDir =>
 			{
 				string testPath = Path.Combine (TI.FindSourceDirectory (), @"Today/TodayExtensionTest.csproj");
@@ -25,6 +28,9 @@ namespace Xamarin.MMP.Tests
 		[Test]
 		public void FinderExtension_SmokeTest ()
 		{
+			if (!PlatformHelpers.CheckSystemVersion (10, 10))
+				return;
+
 			RunMMPTest (tmpDir =>
 			{
 				string testPath = Path.Combine (TI.FindSourceDirectory (), @"Finder/FinderExtensionTest.csproj");
@@ -35,6 +41,9 @@ namespace Xamarin.MMP.Tests
 		[Test]
 		public void ShareExtension_SmokeTest ()
 		{
+			if (!PlatformHelpers.CheckSystemVersion (10, 10))
+				return;
+
 			RunMMPTest (tmpDir =>
 			{
 				string testPath = Path.Combine (TI.FindSourceDirectory (), @"Share/ShareExtensionTest.csproj");