fix: use threading instead of subprocess for Windows provider tests (#639)

[Nikhil172913832]

Pre-flight checklist

• I have read the Contributing Guidelines on pull requests.
• If this is a code change: I have written unit tests and/or added dogfooding pages to fully verify the new behavior.
• If this is a new API or substantial change: the PR has an accompanying issue (closes [CI] Windows Provider Unreachable #639) and the maintainers have approved on my working plan.

Summary

This PR fixes Windows CI failures by refactoring tests/test_match.py to use threading instead of subprocess for starting the Flask provider server. The threading approach matches the pattern used in examples/http/aiohttp_and_flask/test_provider.py and avoids Windows-specific subprocess issues with stderr/stdout buffering and process handling.

Additionally, this re-enables 61 previously disabled compatibility suite tests that were skipped on Windows due to this issue.

Motivation

Issue #639 identified that provider tests fail on Windows because the Flask server started via subprocess.Popen cannot be reached. The subprocess approach has known issues on Windows with:

• Stderr/stdout buffering differences
• Process pipe handling
• URL extraction via regex from stderr

The threading approach eliminates these platform-specific issues and uses pact._util.find_free_port() for dynamic port allocation as requested by maintainers.

Test Plan

• The refactored code follows the exact pattern from existing working examples
• All previously disabled Windows tests have been re-enabled
• CI will validate on Windows with Python 3.10, 3.11, 3.12, and 3.13

🔗 Related issues/PRs

• Closes [CI] Windows Provider Unreachable #639
• Related to PR chore(test): disable failing tests on windows #654 which originally disabled the failing tests

[Copilot]

Pull Request Overview

This PR fixes Windows CI failures by refactoring the Flask provider server startup mechanism from subprocess to threading. The change addresses platform-specific issues with subprocess handling on Windows (stderr/stdout buffering, pipe handling) by adopting the threading pattern already used successfully in examples/http/aiohttp_and_flask/test_provider.py. Additionally, it re-enables 61 compatibility suite tests that were previously disabled on Windows.

Key Changes

• Replaced subprocess-based Flask server startup with thread-based approach in tests/test_match.py
• Implemented dynamic port allocation using pact._util.find_free_port()
• Removed Windows-specific test skips across compatibility suite test files (V1-V4 provider and message tests)

Reviewed Changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
tests/test_match.py	Refactored start_provider() to use threading instead of subprocess, eliminating Windows-specific server startup issues
tests/compatibility_suite/test_v1_provider.py	Removed @pytest.mark.skipif decorators for Windows, re-enabling 28 provider tests
tests/compatibility_suite/test_v2_provider.py	Removed Windows skip decorators, re-enabling 4 V2 provider tests
tests/compatibility_suite/test_v3_provider.py	Removed Windows skip decorators, re-enabling 2 V3 provider tests
tests/compatibility_suite/test_v3_message_producer.py	Removed Windows skip decorators, re-enabling 19 V3 message provider tests
tests/compatibility_suite/test_v3_http_matching.py	Removed Windows skip decorators, re-enabling 8 V3 HTTP matching tests
tests/compatibility_suite/test_v4_provider.py	Removed Windows skip decorators, re-enabling 2 V4 provider tests
tests/compatibility_suite/test_v4_message_provider.py	Removed Windows skip decorators, re-enabling 2 V4 message provider tests

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[Nikhil172913832]

The CI failure is caused by a port already in use in an unrelated test. All Windows provider tests now pass with the threading fix.

[JP-Ellis]

Awesome work! Very neat 🚀