Test Writer Vitest Rtl

Test Writer Skill (Vitest + RTL)

Process

1. Identify what's being tested: pure function → unit test in src/**/*.test.ts next to the source file; component → *.test.tsx next to the component; API route/Server Action → integration test in src/**/__tests__/ or co-located.
2. Cover, at minimum: the happy path, one validation/error path, and any edge case explicitly mentioned by the user or visible in the code (empty arrays, null, boundary numbers).
3. For components, query by accessible role/label/text (getByRole, getByLabelText) — fall back to data-testid only when there is no accessible query available.
4. For async behavior, use findBy* queries or waitFor, never arbitrary setTimeout.
5. For Server Actions/API routes, mock the database layer at the module boundary (e.g. vi.mock('@/server/db')) rather than hitting a real database.
6. Run pnpm test <path> after writing to confirm the test passes (and would have failed before the fix, for regression tests).

Test skeleton

import { describe, it, expect, vi } from "vitest";

describe("<unit under test>", () => {
  it("does the expected thing on the happy path", () => {
    // arrange, act, assert
  });

  it("handles the error/edge case", () => {
    // arrange, act, assert
  });
});

Checklist

• Happy path covered
• At least one failure/edge case covered
• No arbitrary setTimeout/sleep in async tests
• Mocks isolated at module boundary, not deep internals
• pnpm test passes locally