# Test — i18n Coverage & Persistence

**Task**: AZ-465_test_i18n
**Name**: i18n key parity + t() coverage + detector + persistence
**Description**: Implement the 4 blackbox tests that pin the i18n contract: en↔ua key parity (static), `t()` coverage (no raw user-visible strings), boot-time language detector, and persistence across reload.
**Complexity**: 3 points
**Dependencies**: AZ-456_test_infrastructure
**Component**: 03_shared-ui + 10_app-shell (i18n) (Blackbox Tests)
**Tracker**: AZ-465
**Epic**: AZ-455

## Problem

A missing translation key or a hardcoded user-visible string only surfaces when a user switches language — by which point it's a customer-visible defect. Static checks + a behavioral test for detect/persist catch these at commit time.

## Outcome

- 4 scenarios pass per the contract.
- The "no raw strings" check is enforceable in CI and produces a clear allow-list mechanism for legitimate non-i18n text (e.g. brand names).

## Scope

### Included

| Scenario | Profile | Source file | results_report row |
|----------|---------|-------------|--------------------|
| FT-P-22 — i18n key parity en ↔ ua | static | blackbox-tests.md | 45 |
| FT-P-23 — no raw user-visible strings outside `t(...)` | static | blackbox-tests.md | 46 |
| FT-P-24 — i18n detector path used at first boot | fast + e2e | blackbox-tests.md | 47 |
| FT-P-25 — i18n persistence across reload | fast + e2e | blackbox-tests.md | 48 |

### Excluded

- Adding a third language (project is en + ua per scope).
- RTL support (not required by any AC).

## Acceptance Criteria

**AC-1: Key parity**
Static check: `keys(en.json) == keys(ua.json)` (set equality). Test FAILS on any drift.

**AC-2: t() coverage**
Static check via ripgrep + AST walker: every JSX text node and string-literal `aria-*` / `title` / `placeholder` either lives in an i18n key, is in the allow-list (brand names, version strings), or fails the check.

**AC-3: Detector path**
First boot with no persisted language preference: SPA reads `navigator.language` and renders the matching bundle.

**AC-4: Persistence**
After user switches to UA and reloads, the UA bundle is rendered without explicit user action.

## System Under Test Boundary

- System under test: `src/i18n/i18n.ts` + every React component rendering user-visible text.
- Allowed stubs: none beyond the standard test renderer.
- Disallowed: reading the i18n state directly — the test asserts the rendered DOM text.
- Expected observables per rows 45-48.

## Constraints

- Allow-list file lives at `tests/i18n-allowlist.json`; CI enforces it must not grow without a code-review reason.

## Risks & Mitigation

**Risk 1 — AST walker false positives**
- *Risk*: the t() coverage walker may misclassify dynamic strings (e.g. `t(\`key_${id}\`)`) or ternaries.
- *Mitigation*: explicit allow-list per file, plus a comment marker `// i18n-ok: <reason>` honored by the walker.
