[Test Improver] Add unit tests for useI18n composable

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🤖 This PR was created by Test Improver, an automated AI assistant focused on improving test coverage.

Goal and Rationale

shell/composables/useI18n.ts is a key translation composable used throughout the dashboard. It has real branching logic worth testing:

• Module-level state: a store variable that persists across calls, creating interesting interaction patterns
• Initialization guard: throws if called with a null/undefined store
• Null-store fallback in t(): returns the key as-is when the store is unavailable
• Dev-mode warning: logs to console.warn only in dev environments

Despite being globally mocked in jest.setup.js (so other tests can use it without a real store), the composable itself had zero dedicated unit tests.

Approach

The global mock in jest.setup.js would normally prevent direct testing. The solution is to use jest.unmock('@shell/composables/useI18n') combined with jest.resetModules() in beforeEach — this bypasses the global mock and loads the real implementation fresh for each test.

@shell/plugins/i18n is mocked per-test to isolate the stringFor dependency.

Tests Added (9 total)

Group	Test	What it verifies
initialization	valid store	useI18n(store) returns { t } function
initialization	null store	throws 'usI18n() must be called from setup()'
initialization	undefined store	same throw behaviour
t()	full args	delegates to stringFor(store, key, args, raw)
t()	omitted args	passes undefined for args and raw
t()	null store fallback	returns key without calling stringFor
t()	dev-mode warning	console.warn called when process.env.dev is set
t()	no warning outside dev	console.warn not called without process.env.dev
t()	module-level store sharing	t() uses the most recently bound store

Coverage Impact

Before: useI18n.ts — 0 dedicated tests
After: All branches and paths covered (initialization guard, both t() branches, dev-mode conditional)

Reproducibility

YARN_IGNORE_ENGINES=true NODE_OPTIONS=--max_old_space_size=8192 yarn test:ci --testPathPattern=shell/composables/useI18n.test.ts

Test Status

✅ All 9 tests pass
✅ ESLint passes with --max-warnings 0

Warning

Firewall blocked 1 domain

The following domain was blocked by the firewall during workflow execution:

• download.cypress.io

To allow these domains, add them to the network.allowed list in your workflow frontmatter:

network:
  allowed:
    - defaults
    - "download.cypress.io"

See Network Configuration for more information.

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