Add pytest test suite with mocked GitHub API responses

[AshayK003]

Summary

Sets up a proper test harness for the GitHub search crawler. Zero tests was the biggest quality gap — this adds 9 focused tests covering the core wait_for_rate_limit, fetch_page, and crawl_github_algorithm_issues functions.

What was added

tests/conftest.py — shared fixtures

• MockResponse — builds a mock requests.Response with the shape the code expects (status_code, headers, json(), text)
• make_search_result() — builds GitHub Search API result bodies
• mock_requests fixture — patches requests.get with configurable return value
• mock_sleep fixture — patches time.sleep to a no-op so tests finish in ~0.1s instead of minutes
• empty_env / success_response fixtures for common setups

tests/test_main.py — 9 tests covering:

Test	What it verifies
test_uses_reset_ts	wait_for_rate_limit sleeps until X-RateLimit-Reset
test_fallback_60s	Falls back to 60s when no headers present
test_success_returns_response	200 returns the response object
test_403_calls_wait_and_retries	403 → rate-limit wait → retry → success
test_422_returns_none	Rejected query returns None without retry
test_unexpected_status_returns_none	500 returns None
test_timeout_retries	requests.exceptions.Timeout caught and retried
test_max_retries_exceeded	Returns None after exhausting retries
test_produces_output_file	Full crawl writes correct output to results.md

pyproject.toml — added [dev] optional dependency group with pytest>=8 and [tool.pytest.ini_options].

Running

pip install -e ".[dev]"
pytest tests/ -v

Design choices

• Zero external test dependencies — only pytest itself. Uses unittest.mock (stdlib), no pytest-mock or responses needed.
• Mock-based, not integration — no real GitHub API calls, no network. Tests run in ~0.1s.
• time.sleep is patched — rate-limit tests would take minutes of wall time otherwise. With mock_sleep they finish instantly.
• 9/9 pass — verified on Python 3.11.

[Vedant-code]

It's a solid foundation that addresses the "zero tests" problem. Great work. However, it leaves some important paths untested (global state management, _check_rate_limit_before_request, retry-after header).

I am opening a follow-up issue to add the missing tests (especially the global state reset and _check_rate_limit_before_request.