Add integration tests for Microsoft Learn MCP server via Streamable HTTP

[Copilot]

This PR adds integration tests that connect to the Microsoft Learn MCP server at https://learn.microsoft.com/api/mcp using Streamable HTTP transport, validating the SDK's ability to work with production MCP servers.

Changes

New Test Suite: MicrosoftLearnMcpServerTests

Created a comprehensive test class in tests/ModelContextProtocol.Tests/MicrosoftLearnMcpServerTests.cs that validates:

1. Connection and Initialization - Verifies successful connection to the Microsoft Learn MCP server and proper protocol negotiation
2. Tool Discovery - Tests the ability to list available tools from the server
3. Resource Enumeration - Tests listing resources (if available)
4. Prompt Enumeration - Tests listing prompts (if available)
5. Server Ping - Validates basic connectivity via ping

All tests explicitly use HttpTransportMode.StreamableHttp to ensure the Streamable HTTP transport implementation is properly exercised.

Documentation

Added tests/README.md with instructions for running manual tests, including:

• How to run the Microsoft Learn MCP server tests specifically
• How to run all manual tests or exclude them from test runs
• Requirements (networking, .NET 10.0 SDK)

Design Decisions

Manual Execution: All tests are marked with [Trait("Execution", "Manual")] to exclude them from automated CI/CD pipelines, as they depend on an external production service that requires internet connectivity.

Clean Code: Tests use a helper method CreateClientAsync() to reduce code duplication while maintaining readability.

Flexible Assertions: For resource and prompt listing tests, we only assert that the results are non-null rather than non-empty, since we don't know the Microsoft Learn server's configuration.

Running the Tests

# Run just the Microsoft Learn MCP server tests
dotnet test --filter "(FullyQualifiedName~MicrosoftLearnMcpServerTests)"

# Run all manual tests
dotnet test --filter "(Execution=Manual)"

# Exclude manual tests from a test run
dotnet test --filter "(Execution!=Manual)"

These tests provide real-world validation of the C# SDK's Streamable HTTP transport against a production MCP server, complementing the existing unit and integration tests that use local test servers.

Original prompt

Please open a PR that adds a test against the Microsoft Learn MCP server (https://learn.microsoft.com/api/mcp) via streamable HTTP.

---

💬 Share your feedback on Copilot coding agent for the chance to win a $200 gift card! Click here to start the survey.

[Copilot]

@stephentoub Unfortunately, I hit an error while trying to use the custom Copilot setup steps configured for this repository and had to close this PR. The error I am seeing is:

no valid jobs found in copilot-setup-steps.yaml

Once you or someone with the necessary access fixes the problem, please unassign and then reassign issue #0 to me and I'll retry. Thanks!