feat: add unit tests and CI configuration

lib/utils/__tests__/requestId.test.ts

@@ -0,0 +1,61 @@
+import { describe, it, expect, beforeEach } from 'vitest'
+import {
+  generateRequestId,
+  getRequestIdHeader,
+  setLastRequestId,
+  getLastRequestId,
+  clearLastRequestId,
+} from '../requestId'
+
+describe('generateRequestId', () => {
+  it('returns a string starting with REQ', () => {
+    const id = generateRequestId()
+    expect(id).toMatch(/^REQ/)
+  })
+
+  it('contains a timestamp and random segment separated by underscore', () => {
+    const id = generateRequestId()
+    const parts = id.replace('REQ', '').split('_')
+    expect(parts).toHaveLength(2)
+    expect(parts[0].length).toBeGreaterThan(0)
+    expect(parts[1].length).toBeGreaterThan(0)
+  })
+
+  it('generates unique IDs across calls', () => {
+    const ids = new Set(Array.from({ length: 100 }, () => generateRequestId()))
+    expect(ids.size).toBe(100)
+  })
+})
+
+describe('getRequestIdHeader', () => {
+  it('returns X-Request-ID', () => {
+    expect(getRequestIdHeader()).toBe('X-Request-ID')
+  })
+})
+
+describe('lastRequestId storage', () => {
+  beforeEach(() => {
+    clearLastRequestId()
+  })
+
+  it('returns null when no ID has been set', () => {
+    expect(getLastRequestId()).toBeNull()
+  })
+
+  it('stores and retrieves a request ID', () => {
+    setLastRequestId('REQ123_abc')
+    expect(getLastRequestId()).toBe('REQ123_abc')
+  })
+
+  it('overwrites previous ID on set', () => {
+    setLastRequestId('first')
+    setLastRequestId('second')
+    expect(getLastRequestId()).toBe('second')
+  })
+
+  it('clears the stored ID', () => {
+    setLastRequestId('REQ123_abc')
+    clearLastRequestId()
+    expect(getLastRequestId()).toBeNull()
+  })
+})