[FE-68] Establish component testing conventions with reference tests

[mftee]

Overview

Once test discovery is fixed ([FE-65]), the frontend needs a pattern for contributors to follow. @testing-library/jest-dom is already referenced in the Jest setup, and the app uses next-intl with locale routing — so components need providers wrapped correctly or every test fails on a missing intl context.

Tasks

• Add a renderWithProviders test utility wrapping components in NextIntlClientProvider with test messages, plus any auth or theme provider.
• Confirm @testing-library/react and @testing-library/user-event are installed; add them if not.
• Write reference tests for a form component and a data-display component, showing the intended pattern.
• Establish the convention that tests assert user-visible behaviour rather than implementation details.
• Document the pattern in frontend/README.md so contributors have a template.

Acceptance Criteria

• Components render in tests with intl and other providers attached.
• Reference tests exist for contributors to copy.
• The conventions are documented.

Dependencies

Blocked by [FE-65].

Notes for Contributors

Comment below to be assigned.

[phertyameen]

@phertyameen has applied to work on this issue as part of the Stellar Wave Program's 7th wave.

Hello Maintainer, I carefully investigated the issue and have identified the relevant areas for modification. I'll validate the implementation thoroughly before submission.

ℹ️ Repo Maintainers: To accept this application, review their application or assign @phertyameen to this issue.

[drips-wave]

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