[tests] Simplify some logic in mmptest and msbuild tests. (#14400)

Use already existing logic in the Configuration class to find files on disk.

Also remove some dead code and use Path.Combine instead of string
concatenation to compute paths.

Fixes https://github.com/xamarin/maccore/issues/2553.

tests/common/mac/ProjectTestHelpers.cs

@@ -160,17 +160,6 @@ namespace Xamarin.MMP.Tests
 			}
 		}
 
-		public static string AssemblyDirectory
-		{
-			get
-			{
-				string codeBase = Assembly.GetExecutingAssembly ().CodeBase;
-				UriBuilder uri = new UriBuilder (codeBase);
-				string path = Uri.UnescapeDataString (uri.Path);
-				return Path.GetDirectoryName (path);
-			}
-		}
-
 		public static Version FindMonoVersion ()
 		{
 			string output = RunAndAssert ("/Library/Frameworks/Mono.framework/Commands/mono", new [] { "--version" }, "FindMonoVersion");
@@ -453,26 +442,11 @@ namespace Xamarin.MMP.Tests
 				});
 		}
 
-		public static string TestDirectory => Path.Combine (FindRootDirectory (), "..", "tests") + "/";
+		public static string TestDirectory => Path.Combine (Configuration.RootPath, "tests");
 
 		public static string FindSourceDirectory ()
 		{
-			if (Configuration.IsVsts) {
-				// use the working directory from vsts
-				var vstsWorkingDirectory = Environment.GetEnvironmentVariable ("SYSTEM_DEFAULTWORKINGDIRECTORY");
-				var gitDirectory = Path.Combine (vstsWorkingDirectory, ".git");
-				if (Directory.Exists (gitDirectory)) {
-					return Path.Combine (vstsWorkingDirectory, TestDirectory + "common/mac");
-				} else {
-					return Path.Combine (vstsWorkingDirectory, "xamarin-macios" ,TestDirectory + "common/mac");
-				}
-			} else {
-				string codeBase = System.Reflection.Assembly.GetExecutingAssembly ().CodeBase;
-				UriBuilder uri = new UriBuilder (codeBase);
-				string path = Uri.UnescapeDataString (uri.Path);
-				string assemblyDirectory = Path.GetDirectoryName (path);
-				return Path.Combine(assemblyDirectory, TestDirectory + "common/mac");
-			}
+			return Path.Combine (TestDirectory, "common", "mac");
 		}
 
 		public static void CopyDirectory (string src, string target)

tests/mmptest/src/NativeReferencesTests.cs

@@ -51,7 +51,7 @@ namespace Xamarin.MMP.Tests
 			string dylibPath = Path.Combine (tmpDir, "dll/");
 			string filePath = Path.Combine (dylibPath, fileName);
 			Directory.CreateDirectory (dylibPath);
-			File.Copy (Path.Combine (TI.AssemblyDirectory, TI.TestDirectory + "mac-binding-project/bin/SimpleClassDylib.dylib"), filePath);
+			File.Copy (Path.Combine (TI.TestDirectory, "mac-binding-project", "bin", "SimpleClassDylib.dylib"), filePath);
 			return filePath;
 		}
 

tests/msbuild/Xamarin.MacDev.Tests/MSBuild-Smoke.cs

@@ -40,7 +40,7 @@ namespace Xamarin.MMP.Tests
 
 		void TestBCLCore (string tmpDir, string projectName)
 		{
-			var dll = Path.GetFullPath (Path.Combine (TI.TestDirectory + "common", "mac", "System.Collections.Immutable.dll"));
+			var dll = Path.GetFullPath (Path.Combine (TI.TestDirectory, "common", "mac", "System.Collections.Immutable.dll"));
 			string reference = $"<Reference Include=\"System.Collections.Immutable\"><HintPath>{dll}</HintPath></Reference>";
 			string testCode = "var v = System.Collections.Immutable.ImmutableArray.CreateRange (new int [] { 42 });";
 			string projectPath = TI.GenerateEXEProject (new TI.UnifiedTestConfig (tmpDir) { ProjectName = projectName, References = reference, TestCode = testCode });