Fix test suite stability and extended test configuration

[MasumRab]

This PR addresses test stability and configuration issues in the backend test suite.

1. Fixed RateLimiter Flakiness: The test_rate_limiter.py tests were relying on the system clock (datetime.now()), which could lead to failures if tests ran across midnight Pacific Time. This was fixed by using unittest.mock.patch to freeze time during tests.
2. Fixed make extended_tests: The Makefile target extended_tests used the --only-extended flag, which was not recognized by pytest. I added the necessary hooks in backend/tests/conftest.py to register this option and correctly filter tests marked with @pytest.mark.extended.
3. Corrected Test Marking: backend/tests/test_utils_hypothesis.py contains property-based tests that should be part of the extended suite but were missing the marker. I added the marker to ensure they are excluded from the standard test run and included in the extended run.

These changes ensure that make test and make extended_tests work as intended and that the test suite is deterministic.

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PR created automatically by Jules for task 3968941239566233894 started by @MasumRab

Summary by CodeRabbit

• Tests
  • Enhanced test isolation by implementing datetime mocking for rate limiter tests.
  • Introduced CLI option to selectively run extended test suites.
  • Categorized hypothesis-based tests for organized test execution.

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[google-labs-jules]

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[coderabbitai]

Walkthrough

This PR introduces a testing infrastructure enhancement that allows for extended test filtering via a new --only-extended CLI option. Additionally, datetime mocking is added to specific rate limiter tests for deterministic time-based testing, and extended tests are marked to participate in the new filtering mechanism.

Changes

Cohort / File(s)	Summary
Rate Limiter Test Mocking backend/tests/agent/test_rate_limiter.py	Introduces @patch decorator to mock datetime in test_daily_reset_logic and test_no_reset_same_day methods for deterministic time-based testing and fixed timestamp assertions.
Extended Test Infrastructure backend/tests/conftest.py	Adds three pytest hooks (pytest_addoption, pytest_configure, pytest_collection_modifyitems) to implement --only-extended CLI option for selective test execution with custom marker registration.
Extended Test Marking backend/tests/test_utils_hypothesis.py	Applies pytestmark = pytest.mark.extended to mark all tests in module for participation in extended test filtering.

Estimated code review effort

🎯 2 (Simple) | ⏱️ ~10 minutes

Poem

🐰 Datetime dances through the tests,
Extended filters pass the quests,
Pytest hooks hop into the fold,
Testing stories waiting to be told! 📖

🚥 Pre-merge checks | ✅ 3

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and specifically summarizes the main changes: fixing test stability issues in the rate limiter through mocking and implementing extended test configuration support via pytest hooks.
Docstring Coverage	✅ Passed	Docstring coverage is 100.00% which is sufficient. The required threshold is 80.00%.

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✨ Finishing touches

• 📝 Generate docstrings

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix-test-suite-stability-3968941239566233894

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[MasumRab]

Closing as redundant; test suite stability and extended config already fixed in PR #326.

[google-labs-jules]

Closing as redundant; test suite stability and extended config already fixed in PR #326.

Understood. Acknowledging that this work is now obsolete and stopping work on this task.

[MasumRab]

@jules Conflicts detected. Please rebase branch on main using:
git fetch origin && git rebase origin/main
Then push: git push --force-with-lease
Focus on your changed files only - avoid large diff processing.
Report when resolved.