Component View Test Agent

Goal: Create, update, and fix component view tests (*.view.test.tsx) in the MetaMask Mobile codebase using the tests/component-view/ framework.

Use this skill whenever you need to:

• Write a new component view test file
• Update tests after a component or preset has changed
• Diagnose and fix a failing component view test

Your job is to figure out whether the user needs to write a new test, fix a failing test, or update tests after a component/preset change, then follow the corresponding path and open the relevant reference when that path indicates.

Decision tree — which reference to use:

Task → What do you need?
├─ Write new test or update after change
│  → Read component + existing tests
│  → Open references/writing-tests.md (use cases, coverage, renderer/preset, file structure)
│  → If test needs navigation: also open references/navigation-mocking.md
│  → After writing: run tests, then open references/reference.md for self-review
│
├─ Fix failing test
│  → Run: yarn jest -c jest.config.view.js <path> --runInBand --silent --coverage=false
│  → Identify error type → Open references/reference.md (Diagnosing Failures)
│
└─ Run tests or self-review after tests pass
   → Open references/reference.md (Run the Tests, Self-Review Checklist)

Do not read the full reference files until the decision tree or workflow sends you there.

What Are Component View Tests?

Component view tests are integration-level tests that test views through real Redux state — no mocked hooks or selectors. They live alongside the component as ComponentName.view.test.tsx and use a dedicated framework in tests/component-view/.

Key constraint: only Engine and allowed native modules may be mocked (enforced at runtime by app/util/test/testSetupView.js and by ESLint override in .eslintrc.js for **/*.view.test.*).

The Framework at a Glance

tests/component-view/
├── mocks.ts              ← Engine + native mocks (import this first, always)
├── render.tsx            ← renderComponentViewScreen, renderScreenWithRoutes
├── stateFixture.ts       ← StateFixtureBuilder (createStateFixture)
├── platform.ts           ← describeForPlatforms, itForPlatforms (run per iOS/Android)
├── api-mocking/          ← HTTP API mocks (nock) — extensible, one file per feature
├── presets/              ← initialState<Feature>() builders — one file per feature area
└── renderers/            ← render<Feature>View() functions — one file per feature area

Workflow (summary)

• Write new test: Read component and existing tests → list use cases and map to test patterns → check coverage and deduplicate → use or create renderer/preset → write test (use renderScreenWithRoutes if asserting navigation). Every test must have at least one of: fireEvent, waitFor/findBy, store.dispatch/act, or Engine spy (no render-only scenarios). Run tests, then run the self-review checklist in references/reference.md.
• Fix failing test: Run with jest.config.view.js → identify error type from the table in references/reference.md (Diagnosing Failures) → apply the fix (remove disallowed mock, add state override, add preset, wrap in waitFor, add deterministicFiat, etc.) → re-run.
• Update after change: Same as write — review existing tests, extend preset/renderer if needed, update tests, run and self-review.

For full detail (use cases, coverage, presets, route probes, self-review checklist, failure table), use the reference files when the decision tree sends you there.

Run the tests

Always use jest.config.view.js — the default Jest config does not apply component view test rules.

Run tests (no coverage):

yarn jest -c jest.config.view.js <path> --runInBand --silent --coverage=false

Example: yarn jest -c jest.config.view.js app/components/UI/Bridge/Views/BridgeView/BridgeView.view.test.tsx --runInBand --silent --coverage=false

Coverage for a feature folder (use this instead of --coverage to avoid OOM):

yarn test:view:coverage:folder app/components/UI/MyFeature

For run-by-name, watch mode, or other options, see references/reference.md (Run the Tests).

Golden Rules (Enforced)

1. Only mock Engine and allowed native modules — no arbitrary jest.mock() in *.view.test.* files. Allowed:

   • ../../app/core/Engine
   • ../../app/core/Engine/Engine
   • react-native-device-info
   • (these are already handled by tests/component-view/mocks.ts)

2. Drive all behavior through Redux state — no mocking of hooks or selectors. Provide data via state overrides.

3. Reuse presets and renderers — never rebuild the full state manually from scratch.

4. No fake timers — never use jest.useFakeTimers(), jest.advanceTimersByTime(), or jest.useRealTimers().

5. Test behavior, not snapshots — use toBeOnTheScreen(), not.toBeOnTheScreen(), interaction assertions.

6. Follow AAA — Arrange → Act → Assert, blank lines between each section. One test = one user journey or business outcome; multiple chained actions in a single test are fine.

7. No render scenarios — every test must have at least one of: fireEvent, waitFor/findBy, store.dispatch/act, or an Engine spy. Static visibility checks are not tests. See references/writing-tests.md for examples.

8. Use selector ID constants, never raw strings — every getByTestId / findByTestId / queryByTestId must reference a constant from ComponentName.testIds.ts. Create the file if it does not exist.

9. Every view with async data needs one data-completeness test — wait for the load and validate all significant fields of all items in the base mock using within() per row. One per independent async data flow.

10. Filter / segmentation tests must assert both sides — after selecting a filter, assert both what appears (positive findByTestId) and what disappears (negative queryByTestId(...).not.toBeOnTheScreen()).

Reference files (when to use)

Documentation is split by action. Open only the reference that matches what you are doing.

Where self-review and What NOT to Do live: Both are in references/reference.md. Self-review is the checklist you run after tests pass. What NOT to Do is the antipatterns section in the same file. Keeping them there means when you run tests or fix failures you have run commands, the checklist, the failure table, and the antipatterns in one place — open that reference for any run/fix/review task.