Fix dll detection in dotnet test (#50926)

Author: nohwnd

src/Cli/dotnet/Commands/Test/VSTest/TestCommand.cs

@@ -298,11 +298,16 @@ internal static int RunArtifactPostProcessingIfNeeded(string testSessionCorrelat
 
     private static bool ContainsBuiltTestSources(string[] args)
     {
-        foreach (string arg in args)
+        for (int i = 0; i < args.Length; i++)
         {
-            if (!arg.StartsWith("-") &&
-                (arg.EndsWith(".dll", StringComparison.OrdinalIgnoreCase) || arg.EndsWith(".exe", StringComparison.OrdinalIgnoreCase)))
+            string arg = args[i];
+            if (arg.EndsWith(".dll", StringComparison.OrdinalIgnoreCase) || arg.EndsWith(".exe", StringComparison.OrdinalIgnoreCase))
             {
+                var previousArg = i > 0 ? args[i - 1] : null;
+                if (previousArg != null &&  CommonOptions.PropertiesOption.Aliases.Contains(previousArg))
+                {
+                    return false;
+                }
                 return true;
             }
         }

test/dotnet.Tests/CommandTests/Test/GivenDotnetTestBuildsAndRunsTestfromCsproj.cs

@@ -804,6 +804,38 @@ public void ArgumentsEndWithDllOrExeShouldNotFail(string arg)
             }
         }
 
+
+        [Theory]
+        [InlineData("-p:ABC=C:\\my.dll")]
+        [InlineData("/p:ABC=C:\\my.dll")]
+        [InlineData("-property:ABC=C:\\my.dll")]
+        public void PropertiesEndingWithDotDllShouldNotFail(string property)
+        {
+            var testProjectDirectory = CopyAndRestoreVSTestDotNetCoreTestApp([]);
+
+            // Call test
+            // The test will complain about --property:VsTestUseMSBuildOutput=false but
+            // it is the .dll parameter that is causing this. It forces the command to offload work
+            // to vstest.console.exe directly, because it thinks there is some test .dll that we should run
+            // directly, rather than a project file.
+            // Vstest.console.exe will then complain just about the first unknown parameter.
+            CommandResult result = new DotnetTestCommand(Log, disableNewOutput: true)
+                                        .WithWorkingDirectory(testProjectDirectory)
+                                        .Execute(ConsoleLoggerOutputNormal.Concat([property]));
+
+            // Verify
+            if (!TestContext.IsLocalized())
+            {
+                result.StdOut.Should().Contain("Total tests: 2");
+                result.StdOut.Should().Contain("Passed: 1");
+                result.StdOut.Should().Contain("Failed: 1");
+                result.StdOut.Should().Contain("Passed VSTestPassTest");
+                result.StdOut.Should().Contain("Failed VSTestFailTest");
+            }
+
+            result.ExitCode.Should().Be(1);
+        }
+
         private string CopyAndRestoreVSTestDotNetCoreTestApp(object[] parameters, [CallerMemberName] string callingMethod = "")
         {
             // Copy VSTestCore project in output directory of project dotnet-vstest.Tests