Bun Test Conventions

This rule applies to files matching the patterns above.

# Bun Test Conventions

## Rule
All Bun projects MUST use `bun:test` as the primary test runner. Tests must be colocated with source files or in a `__tests__` directory. Test files must match `*.test.ts` or `*.spec.ts`.

## Format
```typescript
import { describe, it, expect, beforeEach, mock } from "bun:test";

describe("ModuleName", () => {
  it("should do expected behavior", () => {
    expect(result).toBe(expected);
  });
});
```

## Good Examples
```typescript
import { describe, it, expect, beforeEach, afterEach, mock } from "bun:test";
import { UserService } from "./user-service";

describe("UserService", () => {
  let service: UserService;

  beforeEach(() => {
    service = new UserService();
  });

  describe("create", () => {
    it("should create a user with valid input", async () => {
      const user = await service.create({
        name: "Alice",
        email: "alice@example.com",
      });
      expect(user.id).toBeDefined();
      expect(user.name).toBe("Alice");
    });

    it("should reject duplicate email addresses", async () => {
      await service.create({ name: "Alice", email: "alice@example.com" });
      expect(
        service.create({ name: "Bob", email: "alice@example.com" })
      ).rejects.toThrow("Email already exists");
    });
  });

  describe("mocking", () => {
    it("should mock fetch calls", async () => {
      const mockFetch = mock(() =>
        Promise.resolve(new Response(JSON.stringify({ ok: true })))
      );
      globalThis.fetch = mockFetch;

      await service.syncExternal();
      expect(mockFetch).toHaveBeenCalledTimes(1);
    });
  });
});
```

## Bad Examples
```typescript
// BAD: Using Jest when Bun has a built-in test runner
import { jest } from "@jest/globals";

// BAD: No describe blocks, flat test structure
test("works", () => { /* ... */ });
test("also works", () => { /* ... */ });

// BAD: No assertion — test always passes
it("should create user", async () => {
  await service.create({ name: "Alice" });
  // Missing expect()!
});
```

## Enforcement
- Configure bunfig.toml with coverage thresholds
- CI runs `bun test --coverage` with minimum thresholds
- Pre-commit hook: `bun test --only-changed`