Summary

E2E tests for the REST→AJAX→bypass fallback chain, ad-blocker simulation (block REST+AJAX → bypass must still track), and complete-block graceful failure.

Motivation

#174 (high): REST + sendBeacon broken — TrackingRestController overwrites raw_post_array for text/plain requests. Ad-blocker bypass is a key differentiating feature.

Dependencies

• Depends on: testing: Set up @wordpress/env Docker environment for reproducible test execution #192 (@wordpress/env)
• Depends on: testing: Correlation ID harness — MU-plugin + TypeScript helper for E2E row isolation #194 (Correlation ID harness)

Implementation

Files to create

• tests/e2e/helpers/transport.ts (skill spec §2.5)
• tests/e2e/specs/transport/transport-fallback.spec.ts

transport.ts route blocking

```typescript
blockTransport('rest'): page.route('/wp-json/slimstat/', r => r.abort())
blockTransport('ajax'): page.route('/admin-ajax.phpaction=slimstat', r => r.abort())
blockTransport('bypass'): page.route('/wp-content/plugins/wp-slimstat/**', r => r.abort())
```

Test scenarios

1. All available → REST used (URL contains /wp-json/slimstat/)
2. Block REST → AJAX fallback (admin-ajax.php) — @link Outbound link tracking broken with REST + sendBeacon #174
3. Block REST+AJAX → bypass transport used (plugin file)
4. Ad-blocker simulation (REST+AJAX blocked) → bypass tracks → DB row confirmed
5. All blocked → 0 DB rows, 0 console errors

Standards

• blockTransport() uses page.route() — never JS-side override (skill spec §2.5)
• Scenario 4 asserts DB row via getCorrelatedRows() — not just request capture
• Transport robustness gate: bypass success rate ≥98% when REST+AJAX blocked (research 01 §C)

Acceptance criteria

• All 5 scenarios pass
• transport.ts fully implemented per skill spec §2.5
• Scenario 4 asserts DB row (not just network request)
• Scenario 5: 0 DB rows + 0 console errors
• S2 detects Outbound link tracking broken with REST + sendBeacon #174 regression if reintroduced

References

• Research 01 §D — Transport robustness, §C — correctness gates
• Skill spec §2.5 (transport.ts)