test: add unit tests for lib/ (validate, auth, storage, email, rate-limit)

49 tests for all 10 Zod schemas in validate.ts, 26 tests for auth (hashPassword,
verifyPassword, createSession, getSession, getCurrentUser, deleteSession), 11 for
storage (magic-byte validation, saveImage, deleteImageFile), 9 for email (sendMail
scenarios), and 6 for rate limiting logic.

test/unit/lib/storage.test.ts

@@ -0,0 +1,126 @@
+import { describe, it, expect, vi, beforeEach } from 'vitest'
+
+const { mockMkdir, mockWriteFile, mockUnlink } = vi.hoisted(() => ({
+  mockMkdir: vi.fn().mockResolvedValue(undefined),
+  mockWriteFile: vi.fn().mockResolvedValue(undefined),
+  mockUnlink: vi.fn().mockResolvedValue(undefined),
+}))
+
+vi.mock('fs/promises', () => ({
+  __esModule: true,
+  default: { mkdir: mockMkdir, writeFile: mockWriteFile, unlink: mockUnlink },
+  mkdir: mockMkdir,
+  writeFile: mockWriteFile,
+  unlink: mockUnlink,
+}))
+
+import { saveImage, validateImageMagicBytes, deleteImageFile } from '@/lib/storage'
+
+function makeJpegBuffer(): Buffer {
+  const b = Buffer.alloc(12)
+  b[0] = 0xff; b[1] = 0xd8; b[2] = 0xff
+  return b
+}
+
+function makePngBuffer(): Buffer {
+  const b = Buffer.alloc(12)
+  b[0] = 0x89; b[1] = 0x50; b[2] = 0x4e; b[3] = 0x47
+  return b
+}
+
+function makeWebpBuffer(): Buffer {
+  const b = Buffer.alloc(12)
+  b[0] = 0x52; b[1] = 0x49; b[2] = 0x46; b[3] = 0x46
+  b[8] = 0x57; b[9] = 0x45; b[10] = 0x42; b[11] = 0x50
+  return b
+}
+
+function makeIcoBuffer(): Buffer {
+  const b = Buffer.alloc(12)
+  b[0] = 0x00; b[1] = 0x00; b[2] = 0x01; b[3] = 0x00
+  return b
+}
+
+function makeFileFromBuffer(buf: Buffer, type: string): File {
+  return new File([new Uint8Array(buf)], 'test.img', { type })
+}
+
+beforeEach(() => {
+  vi.clearAllMocks()
+  mockMkdir.mockResolvedValue(undefined)
+  mockWriteFile.mockResolvedValue(undefined)
+  mockUnlink.mockResolvedValue(undefined)
+})
+
+// ─── validateImageMagicBytes ──────────────────────────────────────────────────
+
+describe('validateImageMagicBytes', () => {
+  it('accepts a valid JPEG', async () => {
+    const file = makeFileFromBuffer(makeJpegBuffer(), 'image/jpeg')
+    expect(await validateImageMagicBytes(file, 'image/jpeg')).toBe(true)
+  })
+
+  it('accepts a valid PNG', async () => {
+    const file = makeFileFromBuffer(makePngBuffer(), 'image/png')
+    expect(await validateImageMagicBytes(file, 'image/png')).toBe(true)
+  })
+
+  it('accepts a valid WebP', async () => {
+    const file = makeFileFromBuffer(makeWebpBuffer(), 'image/webp')
+    expect(await validateImageMagicBytes(file, 'image/webp')).toBe(true)
+  })
+
+  it('accepts a valid ICO', async () => {
+    const file = makeFileFromBuffer(makeIcoBuffer(), 'image/x-icon')
+    expect(await validateImageMagicBytes(file, 'image/x-icon')).toBe(true)
+  })
+
+  it('rejects JPEG buffer declared as PNG', async () => {
+    const file = makeFileFromBuffer(makeJpegBuffer(), 'image/png')
+    expect(await validateImageMagicBytes(file, 'image/png')).toBe(false)
+  })
+
+  it('rejects unknown MIME type', async () => {
+    const file = makeFileFromBuffer(makeJpegBuffer(), 'image/bmp')
+    expect(await validateImageMagicBytes(file, 'image/bmp')).toBe(false)
+  })
+
+  it('rejects a random buffer as JPEG', async () => {
+    const file = makeFileFromBuffer(Buffer.from([0x00, 0x01, 0x02]), 'image/jpeg')
+    expect(await validateImageMagicBytes(file, 'image/jpeg')).toBe(false)
+  })
+})
+
+// ─── saveImage ────────────────────────────────────────────────────────────────
+
+describe('saveImage', () => {
+  it('creates the product directory and writes file', async () => {
+    const buf = Buffer.from('fakeimage')
+    const url = await saveImage('prod-123', buf, 'photo.jpg')
+
+    expect(mockMkdir).toHaveBeenCalledWith(expect.stringContaining('prod-123'), { recursive: true })
+    expect(mockWriteFile).toHaveBeenCalled()
+    expect(url).toMatch(/^\/uploads\/prod-123\//)
+    expect(url).toMatch(/photo\.jpg$/)
+  })
+
+  it('sanitizes filename (removes special chars)', async () => {
+    const buf = Buffer.from('fakeimage')
+    const url = await saveImage('prod-123', buf, 'my photo (1).JPG')
+    expect(url).toMatch(/my_photo__1_\.jpg$/)
+  })
+
+  it('returns a URL starting with /uploads/', async () => {
+    const url = await saveImage('prod-abc', Buffer.from('x'), 'img.png')
+    expect(url).toMatch(/^\/uploads\/prod-abc\//)
+  })
+})
+
+// ─── deleteImageFile ──────────────────────────────────────────────────────────
+
+describe('deleteImageFile', () => {
+  it('calls unlink with the correct path', async () => {
+    await deleteImageFile('/uploads/prod-1/image.jpg')
+    expect(mockUnlink).toHaveBeenCalledWith(expect.stringContaining('/uploads/prod-1/image.jpg'))
+  })
+})