fix: One more test

Author: tmathern

src/c2pa/c2pa.py

@@ -152,12 +152,10 @@ class C2paSigningAlg(enum.IntEnum):
 
 def _guess_mime_type_using_magic_number(file_path: Union[str, Path]) -> Optional[tuple[str, str]]:
     """Guess MIME type by reading file header bytes.
-    Currently supports:
-    - SVG files (start with <?xml or <svg)
-    - Image formats: PNG, JPEG, GIF, TIFF, WebP, AVIF, HEIC, HEIF, DNG
-    - Video formats: MP4, MOV, AVI
-    - Audio formats: MP3, M4A, WAV
-    - Document formats: PDF
+    Currently supports a limited set of files, as this is best effort.
+    You should consider adding extensions to filepaths to ensure we don't
+    have to guess too much.
+
     Args:
         file_path: Path to the file to check
     Returns:
@@ -194,6 +192,8 @@ def _guess_mime_type_using_magic_number(file_path: Union[str, Path]) -> Optional
             return ('webp', 'image/webp')
         elif header.startswith(b'\x00\x00\x00\x20ftypavif'):
             return ('avif', 'image/avif')
+        elif header.startswith(b'\x00\x00\x00\x18ftypmif1') or header.startswith(b'\x00\x00\x00\x18ftypmsf1') or header.startswith(b'\x00\x00\x00\x18ftypheic') or header.startswith(b'\x00\x00\x00\x18ftypheix'):
+            return ('heic', 'image/heic')
 
         # Check for audio formats
         elif header.startswith(b'ID3') or header.startswith(b'\xff\xfb') or header.startswith(b'\xff\xf3'):

…ixtures/extensionless-files/sample1.heif tests/fixtures/extensionless-files/heictests/fixtures/extensionless-files/sample1.heif renamed to tests/fixtures/extensionless-files/heic tests/fixtures/extensionless-files/sample1.heif renamed to tests/fixtures/extensionless-files/heic

@@ -1468,6 +1468,7 @@ def test_guess_mime_type_using_magic_number(self):
             (os.path.join(extensionless_dir, "png"), ('png', 'image/png')),
             (os.path.join(extensionless_dir, "jpg"), ('jpg', 'image/jpeg')),
             (os.path.join(extensionless_dir, "gif"), ('gif', 'image/gif')),
+            (os.path.join(extensionless_dir, "heic"), ('heic', 'image/heic')),
             (os.path.join(extensionless_dir, "tiff"), ('tiff', 'image/tiff')),
             (os.path.join(extensionless_dir, "webp"), ('webp', 'image/webp')),
             (os.path.join(extensionless_dir, "avif"), ('avif', 'image/avif')),