test: add 100% coverage for app/main.py

issuse no:#3 (closed)

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🧾 Description

This MR improves the test coverage of app/main.py from 88% to 100% by adding targeted tests for previously uncovered branches and edge cases.

The goal is to ensure all critical paths, including error handling and conditional logic, are fully validated to prevent regressions.

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✨ What’s Added

🔐 Authentication Tests

• /login redirect to / when auth token exists (302)
• /login?logout=true behavior validation
• No-token login scenario coverage

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🎙️ /api/transcribe Tests

• file_url success flow
• External fetch failure handling
• Valid audio input with non-empty chunks branch

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📝 /api/subtitles Tests

• Valid chunks → successful subtitles generation
• Empty chunks ("[]") + text → synthetic chunk path
• Invalid JSON → returns 400
• generate_subtitles failure → returns 400

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🧪 Additional Coverage

• Covered previously untested conditional branches
• Optional: __main__ execution path (if applicable)

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📊 Result

• Coverage increased: 88% → 100% (app/main.py)
• All tests passing
• Improved reliability and regression safety

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🧪 How to Test

Run: pytest --cov=app.main --cov-report=term-missing

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⚠️ Notes

• External services are mocked for deterministic testing
• Focus on branch coverage, not just line coverage
• No changes to production logic

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✅ Checklist

• Tests added for all uncovered branches
• Coverage reached 100% for app/main.py
• All tests passing
• No breaking changes

Screenshot