Developer Guide: Testing Email Flows End‑to‑End (Sign‑Up, OTP, Reset, Webhooks)
Email flows are product‑critical and easy to break. A single wrong URL, missing token, or deliverability issue can create sign‑up failures or account lockouts. This guide provides a repeatable workflow for end‑to‑end testing.
1) What to test (core checklist)
- Template rendering: desktop + mobile; ensure buttons and text are readable.
- Link correctness: no staging links in production; no mixed http/https.
- Token logic: expiry works; tokens are single‑use when needed.
- Resend policy: rate limits prevent spam and abuse; user messaging is clear.
- Localization: correct language, date formats, and RTL support if applicable.
2) Use a fresh inbox per scenario
Shared test inboxes create confusing leftovers. A fresh disposable inbox per test run keeps results clean.
Create a mailbox: TempMailbox
3) Verify the user journey, not just the email
For each flow (signup verification, OTP, reset):
- Trigger the email from the product UI or API.
- Confirm delivery time (measure median and tail latency).
- Open and verify CTA targets (query parameters, tokens, redirect behavior).
- Confirm post-click results (verified flag set, session created, appropriate success page).
4) Test edge cases intentionally
- Expired token (should fail gracefully)
- Double-click the link (should not break state)
- Resend multiple times (enforce cooldown)
- Wrong email entered then corrected (update path)
5) Observability: track the right metrics
- Send success rate
- Bounce rate and provider rejections
- Verification completion rate
- Time-to-verify distribution
6) Security basics (don’t skip)
- Tokens should be random, scoped, and time‑limited.
- Avoid putting sensitive user identifiers in URLs.
- Invalidate tokens after use when appropriate.
7) Keep QA ethical and safe
Use disposable inboxes for legitimate testing and privacy hygiene. Do not use them for abuse, fraud, or bypassing other services’ rules.
