Bun Test Generator

Generate test files for x4-mono source files using Bun's built-in test runner.

Arguments

The user provides a source file path. If no path given, ask which file to generate tests for.

Test Patterns by Source Location

tRPC Router Tests (apps/api/src/routers/*.ts)

import { describe, test, expect } from 'bun:test';
import { createCallerFactory } from '../trpc';
import { appRouter } from '../routers';
import type { Context } from '../trpc';
import { createMockDb, createTestUser, TEST_USER_ID } from './helpers';

function createTestContext(overrides: Partial<Context> = {}): Context {
  return {
    db: createMockDb(),
    user: null,
    req: new Request('http://localhost:3002'),
    ...overrides,
  };
}

const createCaller = createCallerFactory(appRouter);

For each procedure, test:

• Happy path with valid input
• Invalid input (BAD_REQUEST)
• Unauthenticated access (UNAUTHORIZED) for protected procedures
• Authorization/ownership checks (FORBIDDEN)
• NOT_FOUND for missing resources
• Edge cases (empty results, pagination boundaries)

Middleware Tests (apps/api/src/middleware/*.ts)

import { describe, test, expect } from 'bun:test';
// Test using app.request()

Zod Schema Tests (packages/shared/types/*.ts, packages/shared/utils/validators.ts)

import { describe, test, expect } from 'bun:test';
// Import schemas directly
// Use .safeParse() for validation tests
// Use .parse() for default value tests

For each schema, test:

• Valid input with all required fields
• Valid input with optional fields omitted
• Each required field missing
• Invalid types for each field
• Boundary values (min/max length, min/max number)
• Default values applied correctly
• Enum values accepted/rejected

Unit Tests (apps/api/src/lib/*.ts, packages/shared/utils/*.ts)

import { describe, test, expect } from 'bun:test';
// Direct function import and test

Component Tests (apps/web/src/components/*.tsx)

import { describe, test, expect } from 'bun:test';
// Uses @testing-library/react

Test File Placement

• apps/api/src/routers/foo.ts → apps/api/src/__tests__/foo.test.ts
• apps/api/src/lib/foo.ts → apps/api/src/__tests__/foo.test.ts
• apps/api/src/middleware/foo.ts → apps/api/src/__tests__/foo.test.ts
• packages/shared/utils/foo.ts → packages/shared/utils/foo.test.ts (co-located)
• packages/shared/types/foo.ts → packages/shared/types/foo.test.ts (co-located)
• packages/*/src/foo.ts → packages/*/src/__tests__/foo.test.ts

Conventions

• Always import from bun:test (never jest)
• Use describe blocks grouped by function/procedure name
• Use descriptive test names: "returns X when Y", "throws Z for invalid input"
• Use section comments: // --- functionName ---
• Use toMatchObject for partial error matching: rejects.toMatchObject({ code: "NOT_FOUND" })
• Use createMockDb helper for database mocks in API tests
• Test the tRPC error codes: NOT_FOUND, UNAUTHORIZED, FORBIDDEN, BAD_REQUEST

Workflow

1. Read the source file to understand exports and logic
2. Determine the test pattern based on file location
3. Check for existing test helpers in apps/api/src/__tests__/helpers.ts
4. Generate the test file
5. Run bun test <test-file-path> to verify tests pass