derive-test-shape-from-name

name	derive-test-shape-from-name
description	Given a clear test name, produce given/when/then scaffolding and an assertion structure. Use after derive-test-name-from-behavior to write the actual test body.

Derive a test shape from a name

Given a test name like should reject empty username with a ValidationError, produce a Vitest test body with explicit Given/When/Then sections.

Template

it("should <observable behavior>", () => {
  // Given: <setup, no assertions>
  const input = ...;

  // When: <invoke the SUT>
  const result = ...;

  // Then: <assertions>
  expect(result).toBe(...);
});

Rules

1. Given sets up state but never asserts.
2. When invokes exactly one method or computes one value.
3. Then asserts on the result of When. If you have to compute another value to assert on, the test is doing too much.
4. Prefer concrete inputs over fixtures. expect(validate("")) beats expect(validate(emptyInput)) for readability.

Reusable outside TDD

Used in red phase to scaffold a failing test. Also used by code-review skills to suggest restructuring overly-complex existing tests.