[tests] Category support in TestRunner.NUnit (#1963)

Context: #1534

The `DotNetInterfacesShouldEqualJavaInterfaces()` unit test
*occasionally* fails on certain Android devices, such as:

  * [Oneplus One](https://gist.github.com/pjcollins/50b3036dd4a0b4a4d881a24fe49ab30d):

        09-25 12:36:18.234 I/mono-stdout(26038): [FAIL] : #6.3 (dummy0 not found in Java interfaces)

  * [Samsung S8](https://gist.github.com/pjcollins/5782e1bc225cdf105a75491e23f257d6)

        09-29 10:26:41.754 I/mono-stdout(18006): Expected: 19
        09-29 10:26:41.754 I/mono-stdout(18006): But was: 5

  * [Nexus 6p (API 25)](https://gist.github.com/pjcollins/062f2124e1e76561809193450f97e768)

        09-29 10:26:05.053 I/mono-stdout(32432): Expected: 22
        09-29 10:26:05.053 I/mono-stdout(32432): But was: 4

We do not yet understand what is causing these failures.

That said, QA doesn't want to continue seeing these errors in QA
builds, as reviewing "errors for which we've already filed bugs" is
tedious and annoying, and makes it easier to overlook new issues.

Extend the `[CategoryAttribute]` support in 096210c so that the new
`TestRunner.NUnit` test runner (c4e8165) can also use the same
`$(ExcludeCategories)` MSBuild property to cause tests to be skipped.

Add `[Category("NetworkInterfaces")]` to the
`DotNetInterfacesShouldEqualJavaInterfaces()` test.

Together, these two changes will allow QA to selectively skip the
`DotNetInterfacesShouldEqualJavaInterfaces()` test.

Author: pjcollins

src/Mono.Android/Test/System.Net/NetworkInterfaces.cs

@@ -100,7 +100,7 @@ bool HardwareAddressesAreEqual (byte[] one, byte[] two)
 			}
 		}
 
-		[Test]
+		[Test, Category("NetworkInterfaces")]
 		public void DotNetInterfacesShouldEqualJavaInterfaces ()
 		{
 			List <InterfaceInfo> dotnetInterfaces = GetInfos (MNetworkInterface.GetAllNetworkInterfaces ());

tests/TestRunner.Core/TestInstrumentation.cs

@@ -315,6 +315,17 @@ protected virtual Assembly LoadTestAssembly (string filePath)
 			return Assembly.LoadFrom (filePath);
 		}
 
+		protected Dictionary<string, string> GetStringExtrasFromBundle ()
+		{
+			var filtersFromBundle = new Dictionary<string, string> ();
+			foreach (var key in arguments.KeySet ()) {
+				string value = arguments.GetString (key);
+				if (!string.IsNullOrEmpty (value))
+					filtersFromBundle.Add (key, value);
+			}
+			return filtersFromBundle;
+		}
+
 		protected virtual void ConfigureFilters (TRunner runner)
 		{}
 

tests/TestRunner.NUnit/NUnitTestInstrumentation.cs

@@ -42,6 +42,17 @@ protected override NUnitTestRunner CreateRunner (LogWriter logger, Bundle bundle
 			};
 		}
 
+		IEnumerable<string> GetFilterValuesFromExtras (string key)
+		{
+			Dictionary<string, string> extras = GetStringExtrasFromBundle ();
+			if (extras.ContainsKey (key)) {
+				string filterValue = extras [key];
+				if (!string.IsNullOrEmpty (filterValue))
+					return filterValue.Split (':');
+			}
+			return null;
+		}
+
 		protected override void ConfigureFilters (NUnitTestRunner runner)
 		{
 			base.ConfigureFilters(runner);
@@ -54,9 +65,15 @@ protected override void ConfigureFilters (NUnitTestRunner runner)
 			Log.Info (LogTag, "Configuring test categories to include:");
 			ChainCategoryFilter (IncludedCategories, false, ref filter);
 
+			Log.Info (LogTag, "Configuring test categories to include from extras:");
+			ChainCategoryFilter (GetFilterValuesFromExtras ("include"), false, ref filter);
+
 			Log.Info (LogTag, "Configuring test categories to exclude:");
 			ChainCategoryFilter (ExcludedCategories, true, ref filter);
 
+			Log.Info(LogTag, "Configuring test categories to exclude from extras:");
+			ChainCategoryFilter (GetFilterValuesFromExtras ("exclude"), true, ref filter);
+
 			Log.Info (LogTag, "Configuring tests to exclude (by name):");
 			ChainTestNameFilter (ExcludedTestNames?.ToArray (), ref filter);