Add better error messages for dotnet test with solution/project/directory/dll arguments in Microsoft.Testing.Platform (MTP)

src/Cli/dotnet/Commands/CliCommandStrings.resx

@@ -2605,4 +2605,16 @@ Proceed?</value>
     <value>Tool package download needs confirmation. Run in interactive mode or use the "--yes" command-line option to confirm.</value>
     <comment>{Locked="--yes"}</comment>
   </data>
-</root>
+  <data name="TestCommandUseSolution" xml:space="preserve">
+    <value>Specifying a solution for 'dotnet test' should be via '--solution'.</value>
+  </data>
+  <data name="TestCommandUseProject" xml:space="preserve">
+    <value>Specifying a project for 'dotnet test' should be via '--project'.</value>
+  </data>
+  <data name="TestCommandUseDirectory" xml:space="preserve">
+    <value>Specifying a directory for 'dotnet test' should be via '--directory'.</value>
+  </data>
+  <data name="TestCommandUseTestModules" xml:space="preserve">
+    <value>Specifying dlls or executables for 'dotnet test' should be via '--test-modules'.</value>
+  </data>
+</root>

src/Cli/dotnet/Commands/Test/TestingPlatformCommand.cs

@@ -6,12 +6,13 @@
 using System.CommandLine;
 using Microsoft.DotNet.Cli.Commands.Test.Terminal;
 using Microsoft.DotNet.Cli.Extensions;
+using Microsoft.DotNet.Cli.Utils;
 using Microsoft.TemplateEngine.Cli.Commands;
 using Microsoft.TemplateEngine.Cli.Help;
 
 namespace Microsoft.DotNet.Cli.Commands.Test;
 
-internal partial class TestingPlatformCommand : Command, ICustomHelp
+internal partial class TestingPlatformCommand : System.CommandLine.Command, ICustomHelp
 {
     private MSBuildHandler _msBuildHandler;
     private TerminalTestReporter _output;
@@ -45,7 +46,8 @@ public int Run(ParseResult parseResult)
     private int RunInternal(ParseResult parseResult)
     {
         ValidationUtility.ValidateMutuallyExclusiveOptions(parseResult);
-
+        ValidationUtility.ValidateSolutionOrProjectOrDirectoryOrModulesArePassedCorrectly(parseResult);
+
         PrepareEnvironment(parseResult, out TestOptions testOptions, out int degreeOfParallelism);
 
         InitializeOutput(degreeOfParallelism, parseResult, testOptions.IsHelp);

src/Cli/dotnet/Commands/Test/ValidationUtility.cs

@@ -53,6 +53,7 @@ static void ValidateOptionsIrrelevantToModulesFilter(ParseResult parseResult)
             }
         }
     }
+
     public static bool ValidateBuildPathOptions(BuildOptions buildPathOptions, TerminalTestReporter output)
     {
         PathOptions pathOptions = buildPathOptions.PathOptions;
@@ -76,6 +77,47 @@ public static bool ValidateBuildPathOptions(BuildOptions buildPathOptions, Termi
         return true;
     }
 
+    /// <summary>
+    /// Validates that arguments requiring specific command-line switches are used correctly for Microsoft.Testing.Platform.
+    /// Provides helpful error messages when users provide file/directory arguments without proper switches.
+    /// </summary>
+    public static void ValidateSolutionOrProjectOrDirectoryOrModulesArePassedCorrectly(ParseResult parseResult)
+    {
+        if (Environment.GetEnvironmentVariable("DOTNET_TEST_DISABLE_SWITCH_VALIDATION") is "true" or "1")
+        {
+            // In case there is a valid case, users can opt-out.
+            // Note that the validation here is added to have a "better" error message for scenarios that will already fail.
+            // So, disabling validation is okay if the user scenario is valid.
+            return;
+        }
+
+        foreach (string token in parseResult.UnmatchedTokens)
+        {
+            // Check for .sln files
+            if ((token.EndsWith(".sln", StringComparison.OrdinalIgnoreCase) ||
+                token.EndsWith(".slnx", StringComparison.OrdinalIgnoreCase)) && File.Exists(token))
+            {
+                throw new GracefulException(CliCommandStrings.TestCommandUseSolution);
+            }
+            else if ((token.EndsWith(".csproj", StringComparison.OrdinalIgnoreCase) ||
+                     token.EndsWith(".vbproj", StringComparison.OrdinalIgnoreCase) ||
+                     token.EndsWith(".fsproj", StringComparison.OrdinalIgnoreCase)) && File.Exists(token))
+            {
+                throw new GracefulException(CliCommandStrings.TestCommandUseProject);
+            }
+            else if (Directory.Exists(token))
+            {
+                throw new GracefulException(CliCommandStrings.TestCommandUseDirectory);
+            }
+            else if ((token.EndsWith(".dll", StringComparison.OrdinalIgnoreCase) ||
+                      token.EndsWith(".exe", StringComparison.OrdinalIgnoreCase)) &&
+                     File.Exists(token))
+            {
+                throw new GracefulException(CliCommandStrings.TestCommandUseTestModules);
+            }
+        }
+    }
+
     private static bool ValidateSolutionFilePath(string filePath, TerminalTestReporter output)
     {
         if (!CliConstants.SolutionExtensions.Contains(Path.GetExtension(filePath)))