[tests] Use correct test result for adb hosts (#1365)

Certain deployment targets require us to fix up an external storage
path before we can pull it via adb (see `ToAdbPath()` comments for
more details). We should only attempt to fix up this path *after*
writing our test result, as our application context will not
recognize it as a valid file path.

Fixes the following error:

	Error: System.IO.DirectoryNotFoundException: Could not find a part of the path "/mnt/shell/emulated/0/Android/data/Xamarin.Android.Bcl_Tests/files/Documents/TestResults.xUnit.xml".
	  at System.IO.FileStream..ctor (System.String path, System.IO.FileMode mode, System.IO.FileAccess access, System.IO.FileShare share, System.Int32 bufferSize, System.Boolean anonymous, System.IO.FileOptions options) [0x00177] in /Users/builder/jenkins/workspace/xamarin-android-d15-7/xamarin-android/external/mono/mcs/class/corlib/System.IO/FileStream.cs:223 
	  at System.IO.FileStream..ctor (System.String path, System.IO.FileMode mode, System.IO.FileAccess access, System.IO.FileShare share, System.Int32 bufferSize, System.IO.FileOptions options) [0x00000] in /Users/builder/jenkins/workspace/xamarin-android-d15-7/xamarin-android/external/mono/mcs/class/corlib/System.IO/FileStream.cs:106 
	  at System.IO.FileStream..ctor (System.String path, System.IO.FileMode mode, System.IO.FileAccess access, System.IO.FileShare share, System.Int32 bufferSize, System.Boolean useAsync) [0x00000] in /Users/builder/jenkins/workspace/xamarin-android-d15-7/xamarin-android/external/mono/mcs/class/corlib/System.IO/FileStream.cs:101 
	  at (wrapper remoting-invoke-with-check) System.IO.FileStream..ctor(string,System.IO.FileMode,System.IO.FileAccess,System.IO.FileShare,int,bool)
	  at System.Xml.XmlWriterSettings.CreateWriter (System.String outputFileName) [0x00051] in /Users/builder/jenkins/workspace/xamarin-android-d15-7/xamarin-android/external/mono/mcs/class/referencesource/System.Xml/System/Xml/Core/XmlWriterSettings.cs:464 
	  at System.Xml.XmlWriter.Create (System.String outputFileName, System.Xml.XmlWriterSettings settings) [0x0000a] in /Users/builder/jenkins/workspace/xamarin-android-d15-7/xamarin-android/external/mono/mcs/class/referencesource/System.Xml/System/Xml/Core/XmlWriter.cs:610 
	  at Xamarin.Android.UnitTests.XUnit.XUnitTestRunner.WriteResultsToFile ()
	  at Xamarin.Android.UnitTests.TestInstrumentation`1[TRunner].RunTests (Android.OS.Bundle& results)
	  at Xamarin.Android.UnitTests.TestInstrumentation`1[TRunner].OnStart ()
	UNHANDLED EXCEPTION:
	Java.Lang.NullPointerException: Exception of type 'Java.Lang.NullPointerException' was thrown.
	  at System.Runtime.ExceptionServices.ExceptionDispatchInfo.Throw () [0x0000c] in /Users/builder/jenkins/workspace/xamarin-android-d15-7/xamarin-android/external/mono/mcs/class/referencesource/mscorlib/system/runtime/exceptionservices/exceptionservicescommon.cs:152 
	  at Java.Interop.JniEnvironment+InstanceMethods.CallNonvirtualVoidMethod (Java.Interop.JniObjectReference instance, Java.Interop.JniObjectReference type, Java.Interop.JniMethodInfo method, Java.Interop.JniArgumentValue* args) [0x00089] in <1c16e67a812b475a9ae6b6e26eed9097>:0 
	  at Java.Interop.JniPeerMembers+JniInstanceMethods.InvokeVirtualVoidMethod (System.String encodedMember, Java.Interop.IJavaPeerable self, Java.Interop.JniArgumentValue* parameters) [0x0005d] in <1c16e67a812b475a9ae6b6e26eed9097>:0 
	  at Android.App.Instrumentation.Finish (Android.App.Result resultCode, Android.OS.Bundle results) [0x0003a] in /Users/builder/data/lanes/5945/28b08da2/source/monodroid/external/xamarin-android/src/Mono.Android/obj/Release/android-27/mcw/Android.App.Instrumentation.cs:1366 
	  at Xamarin.Android.UnitTests.TestInstrumentation`1[TRunner].OnStart ()
	  at Android.App.Instrumentation.n_OnStart (System.IntPtr jnienv, System.IntPtr native__this) [0x00008] in /Users/builder/data/lanes/5945/28b08da2/source/monodroid/external/xamarin-android/src/Mono.Android/obj/Release/android-27/mcw/Android.App.Instrumentation.cs:1729 
	  at (wrapper dynamic-method) System.Object.60d1c0b0-3a21-410a-9b3a-12e201b965fe(intptr,intptr)
	  --- End of managed Java.Lang.NullPointerException stack trace ---
	java.lang.NullPointerException
		at android.app.Instrumentation.finish(Instrumentation.java:213)
		at md58bfc2187967f55be2f50e366b0d6b91f.TestInstrumentation_1.n_onStart(Native Method)
		at md58bfc2187967f55be2f50e366b0d6b91f.TestInstrumentation_1.onStart(TestInstrumentation_1.java:35)
		at android.app.Instrumentation$InstrumentationThread.run(Instrumentation.java:1792)

tests/TestRunner.Core/TestInstrumentation.cs

@@ -257,7 +257,7 @@ bool RunTests (ref Bundle results)
 			results.PutLong (ResultInconclusiveTests, runner.InconclusiveTests);
 			results.PutLong (ResultTotalTests, runner.TotalTests);
 			results.PutLong (ResultFilteredTests, runner.FilteredTests);
-			results.PutString (ResultResultsFilePath, resultsFilePath);
+			results.PutString (ResultResultsFilePath, ToAdbPath (resultsFilePath));
 
 			Log.Info (LogTag, $"Passed: {runner.PassedTests}, Failed: {runner.FailedTests}, Skipped: {runner.SkippedTests}, Inconclusive: {runner.InconclusiveTests}, Total: {runner.TotalTests}, Filtered: {runner.FilteredTests}");
 
@@ -364,5 +364,26 @@ protected HashSet<string> LoadExcludedTests (TextReader reader)
 				excludedTestNames.Add (line);
 			} while (true);
 		}
+
+		// On some Android targets, the external storage directory is "emulated",
+		// in which case the paths used on-device by the application are *not*
+		// paths that can be used off-device with `adb pull`.
+		// For example, `Contxt.GetExternalFilesDir()` may return `/storage/emulated/foo`,
+		// but `adb pull /storage/emulated/foo` will *fail*; instead, we may need
+		// `adb pull /mnt/shell/emulated/foo`.
+		// The `$EMULATED_STORAGE_SOURCE` and `$EMULATED_STORAGE_TARGET` environment
+		// variables control the "on-device" (`$EMULATED_STORAGE_TARGET`) and
+		// "off-device" (`$EMULATED_STORAGE_SOURCE`) directory prefixes
+		string ToAdbPath (string path)
+		{
+			string source = global::System.Environment.GetEnvironmentVariable ("EMULATED_STORAGE_SOURCE")?.Trim ();
+			string target = global::System.Environment.GetEnvironmentVariable ("EMULATED_STORAGE_TARGET")?.Trim ();
+
+			if (!String.IsNullOrEmpty (source) && !String.IsNullOrEmpty (target) && path.StartsWith (target, StringComparison.Ordinal)) {
+				return path.Replace (target, source);
+			}
+
+			return path;
+		}
 	}
 }

tests/TestRunner.Core/TestRunner.cs

@@ -107,28 +107,7 @@ protected virtual string GetResultsFilePath ()
 			if (!usePathFile && !Directory.Exists (resultsPath))
 				Directory.CreateDirectory (resultsPath);
 
-			return ToAdbPath (Path.Combine (resultsPath, ResultsFileName));
-		}
-
-		// On some Android targets, the external storage directory is "emulated",
-		// in which case the paths used on-device by the application are *not*
-		// paths that can be used off-device with `adb pull`.
-		// For example, `Contxt.GetExternalFilesDir()` may return `/storage/emulated/foo`,
-		// but `adb pull /storage/emulated/foo` will *fail*; instead, we may need
-		// `adb pull /mnt/shell/emulated/foo`.
-		// The `$EMULATED_STORAGE_SOURCE` and `$EMULATED_STORAGE_TARGET` environment
-		// variables control the "on-device" (`$EMULATED_STORAGE_TARGET`) and
-		// "off-device" (`$EMULATED_STORAGE_SOURCE`) directory prefixes
-		string ToAdbPath (string path)
-		{
-			string source = global::System.Environment.GetEnvironmentVariable ("EMULATED_STORAGE_SOURCE")?.Trim ();
-			string target = global::System.Environment.GetEnvironmentVariable ("EMULATED_STORAGE_TARGET")?.Trim ();
-
-			if (!String.IsNullOrEmpty (source) && !String.IsNullOrEmpty (target) && path.StartsWith (target, StringComparison.Ordinal)) {
-				return path.Replace (target, source);
-			}
-
-			return path;
+			return Path.Combine (resultsPath, ResultsFileName);
 		}
 	}
 }