test: add test for image file handling in read command

tests/basic/test_commands.py

@@ -875,6 +875,34 @@ class TestCommands(TestCase):
             os.unlink(external_file1_path)
             os.unlink(external_file2_path)
 
+    def test_cmd_read_only_with_image_file(self):
+        with GitTemporaryDirectory() as repo_dir:
+            io = InputOutput(pretty=False, fancy_input=False, yes=False)
+            coder = Coder.create(self.GPT35, None, io)
+            commands = Commands(io, coder)
+
+            # Create a test image file
+            test_file = Path(repo_dir) / "test_image.jpg"
+            test_file.write_text("Mock image content")
+
+            # Test with non-vision model
+            commands.cmd_read_only(str(test_file))
+            self.assertEqual(len(coder.abs_read_only_fnames), 0)
+
+            # Test with vision model
+            vision_model = Model("gpt-4-vision-preview")
+            vision_coder = Coder.create(vision_model, None, io)
+            vision_commands = Commands(io, vision_coder)
+
+            vision_commands.cmd_read_only(str(test_file))
+            self.assertEqual(len(vision_coder.abs_read_only_fnames), 1)
+            self.assertTrue(
+                any(
+                    os.path.samefile(str(test_file), fname)
+                    for fname in vision_coder.abs_read_only_fnames
+                )
+            )
+
     def test_cmd_read_only_with_glob_pattern(self):
         with GitTemporaryDirectory() as repo_dir:
             io = InputOutput(pretty=False, fancy_input=False, yes=False)