test: 添加测试支持

src/utils/__tests__/imageResizer.test.ts

@@ -0,0 +1,93 @@
+/**
+ * Tests for fix: 修复截图 MIME 类型硬编码导致 API 拒绝的问题
+ *
+ * macOS screencapture outputs PNG but the code was hardcoding "image/jpeg",
+ * causing API errors. The fix detects the actual format from magic bytes.
+ */
+import { describe, expect, test } from 'bun:test'
+import { detectImageFormatFromBase64, detectImageFormatFromBuffer } from '../imageResizer.js'
+
+// ── Magic byte helpers ────────────────────────────────────────────────────────
+
+/** PNG magic bytes: 0x89 0x50 0x4E 0x47 ... */
+const PNG_HEADER = Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a])
+/** JPEG magic bytes: 0xFF 0xD8 0xFF */
+const JPEG_HEADER = Buffer.from([0xff, 0xd8, 0xff, 0xe0, 0x00, 0x10])
+/** GIF magic bytes: GIF89a */
+const GIF_HEADER = Buffer.from([0x47, 0x49, 0x46, 0x38, 0x39, 0x61])
+/** WebP: RIFF....WEBP */
+const WEBP_HEADER = Buffer.from([
+  0x52, 0x49, 0x46, 0x46, // RIFF
+  0x00, 0x00, 0x00, 0x00, // file size (placeholder)
+  0x57, 0x45, 0x42, 0x50, // WEBP
+])
+
+function toBase64(buf: Buffer): string {
+  return buf.toString('base64')
+}
+
+// ── detectImageFormatFromBuffer ───────────────────────────────────────────────
+
+describe('detectImageFormatFromBuffer', () => {
+  test('detects PNG from magic bytes', () => {
+    expect(detectImageFormatFromBuffer(PNG_HEADER)).toBe('image/png')
+  })
+
+  test('detects JPEG from magic bytes', () => {
+    expect(detectImageFormatFromBuffer(JPEG_HEADER)).toBe('image/jpeg')
+  })
+
+  test('detects GIF from magic bytes', () => {
+    expect(detectImageFormatFromBuffer(GIF_HEADER)).toBe('image/gif')
+  })
+
+  test('detects WebP from RIFF+WEBP magic bytes', () => {
+    expect(detectImageFormatFromBuffer(WEBP_HEADER)).toBe('image/webp')
+  })
+
+  test('returns image/png as default for unknown format', () => {
+    const unknown = Buffer.from([0x00, 0x01, 0x02, 0x03])
+    expect(detectImageFormatFromBuffer(unknown)).toBe('image/png')
+  })
+
+  test('returns image/png for buffer shorter than 4 bytes', () => {
+    expect(detectImageFormatFromBuffer(Buffer.from([0x89]))).toBe('image/png')
+    expect(detectImageFormatFromBuffer(Buffer.alloc(0))).toBe('image/png')
+  })
+})
+
+// ── detectImageFormatFromBase64 ───────────────────────────────────────────────
+
+describe('detectImageFormatFromBase64', () => {
+  test('detects PNG from base64-encoded PNG header', () => {
+    expect(detectImageFormatFromBase64(toBase64(PNG_HEADER))).toBe('image/png')
+  })
+
+  test('detects JPEG from base64-encoded JPEG header', () => {
+    expect(detectImageFormatFromBase64(toBase64(JPEG_HEADER))).toBe('image/jpeg')
+  })
+
+  test('detects GIF from base64-encoded GIF header', () => {
+    expect(detectImageFormatFromBase64(toBase64(GIF_HEADER))).toBe('image/gif')
+  })
+
+  test('detects WebP from base64-encoded WebP header', () => {
+    expect(detectImageFormatFromBase64(toBase64(WEBP_HEADER))).toBe('image/webp')
+  })
+
+  test('returns image/png as default for empty string', () => {
+    expect(detectImageFormatFromBase64('')).toBe('image/png')
+  })
+
+  test('returns image/png for invalid base64', () => {
+    // Should not throw — gracefully defaults
+    expect(detectImageFormatFromBase64('!!!not-base64!!!')).toBe('image/png')
+  })
+
+  test('macOS screencapture PNG is not misidentified as JPEG', () => {
+    // This is the core regression: PNG data must NOT return image/jpeg
+    const result = detectImageFormatFromBase64(toBase64(PNG_HEADER))
+    expect(result).not.toBe('image/jpeg')
+    expect(result).toBe('image/png')
+  })
+})