Catching bugs before they bite: Django Testing

Week 5: Testing Everything—Unit, Integration, Functional & Beyond

TL;DR

I wrote and ran unit, integration, functional, smoke, and regression tests for Vimist’s services and endpoints—uncovered atomicity and signal bugs that only appeared on a live server.

1. Unit Tests for Core Services

• What I tested:
  • process_sale
  • process_purchase
  • Credit account adjustments
• Goal: Verify business logic in isolation before touching the database or HTTP layer.

2. Integration Tests Across Services

• Focus: Ensure related functions play nicely together.
• Scenarios:
  • Sale → inventory decrement
  • Purchase → inventory increment
  • Credit sale limits & repayments
  • Mixed payment methods: Cash, M-Pesa, Credit

3. Functional Flow Verification

• End-to-end checks:
  • User signup + alert notification
  • Making purchases & payments
  • Low-stock and overdue payment alerts

4. Manual “Live” Testing Catches What Code Can’t

• How: Hit the real API server with Postman/cURL.
• Findings:
  • Sales weren’t fully atomic—errors raised but records still saved.
  • Duplicate credit entries when serializers and signals both processed transactions.

Lesson: Unit & integration tests are great—but manual/smoke tests on the live server are invaluable for catching signal- and transaction-related bugs.

Final Thoughts

Testing isn’t just a checkbox, it’s your fastest path to confidence and fewer late-night fire drills.

Next up: automating CI/CD pipelines to run these tests on every push.

See you in Week 6!

-vn-vision