Add tests for VideoEncoder fileName-related error checks in torchcodec (#909)

Summary:

Added tests for
- When an invalid file extension is passed in as fileName
- When a non-existent path is passed in as fileName

Differential Revision: D83087084

Author: mollyxu

src/torchcodec/_core/Encoder.cpp

@@ -574,8 +574,6 @@ VideoEncoder::VideoEncoder(
       fileName,
       ", make sure it's a valid path? ",
       getFFMPEGErrorStringFromErrorCode(status));
-  // TODO-VideoEncoder: Add tests for above fileName related checks
-
   initializeEncoder(videoStreamOptions);
 }
 

test/test_ops.py

@@ -1268,6 +1268,26 @@ def test_bad_input(self, tmp_path):
                 filename=output_file,
             )
 
+        with pytest.raises(
+            RuntimeError,
+            match=r"Couldn't allocate AVFormatContext. The destination file is ./file.bad_extension, check the desired extension\?",
+        ):
+            encode_video_to_file(
+                frames=torch.randint(high=255, size=(10, 3, 60, 60), dtype=torch.uint8),
+                frame_rate=10,
+                filename="./file.bad_extension",
+            )
+
+        with pytest.raises(
+            RuntimeError,
+            match=r"avio_open failed. The destination file is ./bad/path.mp3, make sure it's a valid path\?",
+        ):
+            encode_video_to_file(
+                frames=torch.randint(high=255, size=(10, 3, 60, 60), dtype=torch.uint8),
+                frame_rate=10,
+                filename="./bad/path.mp3",
+            )
+
     def decode(self, file_path) -> torch.Tensor:
         decoder = create_from_file(str(file_path), seek_mode="approximate")
         add_video_stream(decoder)