Add better error messages for dotnet test with file/directory arguments in Microsoft Testing Platform (MTP)

[Copilot]

When users run dotnet test with file or directory arguments as positional parameters, they previously received confusing MSBuild or VSTest errors. This PR adds validation to detect these patterns and provide helpful guidance for Microsoft Testing Platform (MTP) users.

Problem

Users often try commands like:

• dotnet test MySolution.sln
• dotnet test MyProject.csproj
• dotnet test path/to/directory
• dotnet test test.dll

These would result in confusing errors like:

• "Solution file error MSB5010: No file format header found"
• "Project file could not be loaded. Data at the root level is invalid"
• "Specify a project or solution file. The current working directory does not contain a project or solution file"

Solution

Added validation in the Microsoft Testing Platform command path (TestingPlatformCommand.cs) to detect file/directory arguments and suggest using the appropriate flags directly (--solution, --project, --directory, --test-modules).

Examples

Before:

$ dotnet test MySolution.sln
MySolution.sln : Solution file error MSB5010: No file format header found.

After (when MTP is enabled):

$ dotnet test MySolution.sln
Solution file 'MySolution.sln' was provided as a positional argument.
Use the --solution flag: dotnet test --solution MySolution.sln

Implementation Details

• Validation only applies when Microsoft Testing Platform is enabled
• Validation triggers for files that actually exist to avoid interfering with MSBuild's normal error handling
• Non-breaking change - existing functionality preserved for VSTest path
• Comprehensive test coverage for all validation scenarios in the MTP command path
• VSTest path (TestCommand.cs) remains unchanged to preserve existing behavior

Fixes #49710.

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[Youssef1313]

This file is for VSTest. We need to update the implementation for MTP instead, which is in TestingPlatformCommand.

[Youssef1313]

@copilot This file is for VSTest. We need to update the implementation for MTP instead, which is in TestingPlatformCommand.

[Copilot]

You're absolutely correct. I've now implemented the validation logic in TestingPlatformCommand.cs as well to ensure consistent error messages regardless of which test runner is being used. The implementation provides appropriate guidance for MTP users to use the correct flags (--solution, --project, --directory, --test-modules) when they provide file/directory arguments as positional parameters. Commit 455bd3b addresses this by adding the validation to both command paths.

[Youssef1313]

@copilot Revert all changes in src/Cli/dotnet/Commands/Test/TestCommand.cs

[Copilot]

@copilot Revert all changes in src/Cli/dotnet/Commands/Test/TestCommand.cs

All changes in TestCommand.cs have been reverted. Commit 8c23e19.

[Copilot]

Pull Request Overview

This PR adds validation for Microsoft Testing Platform (MTP) to provide better error messages when users run dotnet test with file or directory arguments as positional parameters instead of using the appropriate command-line flags.

• Validates file/directory arguments and suggests using proper flags (--solution, --project, --directory, --test-modules)
• Adds comprehensive test coverage for all validation scenarios in the MTP command path
• Updates localization files with new error messages

Reviewed Changes

Copilot reviewed 17 out of 17 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
src/Cli/dotnet/Commands/Test/ValidationUtility.cs	Adds new validation method to detect file/directory arguments and provide helpful error messages
src/Cli/dotnet/Commands/Test/TestingPlatformCommand.cs	Integrates validation into the MTP command execution path
src/Cli/dotnet/Commands/CliCommandStrings.resx	Adds English resource strings for the new error messages
src/Cli/dotnet/Commands/xlf/*.xlf	Updates localization files with new error message entries marked as "new"
test/dotnet.Tests/CommandTests/Test/TestCommandValidationTests.cs	Adds comprehensive test coverage for validation scenarios

[Copilot]

Grammar error: 'a dlls' should be 'dlls' (remove the article 'a' before the plural noun).

Suggested change

	<value>Specifying a dlls or executables for 'dotnet test' should be via '--test-modules'.</value>
	<value>Specifying dlls or executables for 'dotnet test' should be via '--test-modules'.</value>

[Youssef1313]

@copilot Please update "Specifying a dlls" to "Specifying dlls" (remove the "a") in the resx and all xlf files.

[Copilot]

Fixed the grammar error by removing "a" from "Specifying a dlls" in the .resx file and all .xlf files. Commit 5d6eab3.