TDD Workflow

This skill enforces Test-Driven Development for the packages/server package.

Workflow

1. Red: Write a Failing Test First

Before writing any implementation code, create or update a test file in packages/server/test/:

// Example test structure
import { describe, it, expect } from "vitest";
import dedent from "dedent";

describe("featureName", () => {
  it("should do the expected behavior", () => {
    // Arrange
    const input = ...;

    // Act
    const result = functionUnderTest(input);

    // Assert
    expect(result).toBe(expectedValue);
  });
});

Run the test to confirm it fails:

cd packages/server && pnpm test -- --run test/<test-file>.test.ts

The test MUST fail before proceeding. If it passes, the test is not testing new behavior.

2. Green: Write Minimal Implementation

Write the minimum code needed to make the test pass:

• Only implement what's required to pass the test
• Don't add extra features or optimizations
• Don't refactor yet

Run the test again:

cd packages/server && pnpm test -- --run test/<test-file>.test.ts

The test MUST pass before proceeding.

3. Refactor: Clean Up the Code

Now that tests are green, improve the code:

• Remove duplication
• Improve naming
• Simplify logic
• Ensure consistent style

Run tests after each refactoring step to ensure nothing breaks:

cd packages/server && pnpm test

Test File Conventions

• Test files: packages/server/test/*.test.ts
• Use vitest with describe, it, expect
• Use dedent for multi-line string fixtures
• Import types from @openapi-lsp/core/openapi

Example TDD Session

Task: Add validation for empty arrays

Step 1 - Red:

it("should return error for empty array", () => {
  const result = validate([]);
  expect(result.ok).toBe(false);
  expect(result.error).toBe("Array cannot be empty");
});

Run test → FAIL ✗

Step 2 - Green:

function validate(arr: unknown[]) {
  if (arr.length === 0) {
    return { ok: false, error: "Array cannot be empty" };
  }
  return { ok: true };
}

Run test → PASS ✓

Step 3 - Refactor:

function validate(arr: unknown[]): Result<void, string> {
  if (arr.length === 0) {
    return Err("Array cannot be empty");
  }
  return Ok(undefined);
}

Run test → PASS ✓

Running Tests

# Run specific test file
cd packages/server && pnpm test -- --run test/serializeSchema.test.ts

# Run all tests
npm run test

# Run tests in watch mode (during development)
cd packages/server && pnpm test