Add MP4 upload support

tests/test_main_cli.py

@@ -4,7 +4,7 @@ from __future__ import annotations
 
 from src.audio_separation import DEFAULT_MIX_MODE
 
-from main import _build_translation_config, build_parser
+from main import _build_translation_config, _validate_source_args, build_parser
 
 
 def test_parser_accepts_lmstudio_flags():
@@ -69,3 +69,37 @@ def test_parser_defaults_to_instrumental_only_mix_mode():
     args = parser.parse_args(["https://youtube.com/watch?v=demo"])
 
     assert args.mix_mode == DEFAULT_MIX_MODE
+
+
+def test_parser_accepts_local_input_file_without_url():
+    parser = build_parser()
+
+    args = parser.parse_args(["--input-file", "demo.mp4", "--lang", "fr"])
+
+    assert args.url is None
+    assert args.input_file == "demo.mp4"
+    assert args.lang == "fr"
+
+
+def test_validate_source_args_rejects_missing_source():
+    parser = build_parser()
+    args = parser.parse_args([])
+
+    try:
+        _validate_source_args(args)
+    except SystemExit as exc:
+        assert "Provide either" in str(exc)
+    else:
+        raise AssertionError("Expected SystemExit for missing source")
+
+
+def test_validate_source_args_rejects_two_sources():
+    parser = build_parser()
+    args = parser.parse_args(["https://youtube.com/watch?v=demo", "--input-file", "demo.mp4"])
+
+    try:
+        _validate_source_args(args)
+    except SystemExit as exc:
+        assert "not both" in str(exc)
+    else:
+        raise AssertionError("Expected SystemExit for two sources")