added test for choose_fence

tests/test_coder.py

@@ -239,5 +239,30 @@ class TestCoder(unittest.TestCase):
         coder.run(with_message="hi")
         self.assertEqual(len(coder.abs_fnames), 1)
 
+    def test_choose_fence(self):
+        # Create a few temporary files
+        _, file1 = tempfile.mkstemp()
+
+        with open(file1, "wb") as f:
+            f.write(b"this contains ``` backticks")
+
+        files = [file1]
+
+        # Initialize the Coder object with the mocked IO and mocked repo
+        coder = Coder.create(
+            models.GPT4, None, io=InputOutput(), openai_api_key="fake_key", fnames=files
+        )
+
+        def mock_send(*args, **kwargs):
+            coder.partial_response_content = "ok"
+            coder.partial_response_function_call = dict()
+
+        coder.send = MagicMock(side_effect=mock_send)
+
+        # Call the run method with a message
+        coder.run(with_message="hi")
+
+        self.assertNotEqual(coder.fence[0], "```")
+
     if __name__ == "__main__":
         unittest.main()