aider: Added a test function for the check_for_file_mentions method in tests/test_coder.py.

# Context:
USER: write a test for check_for_file_mentions
ASSISTANT: To write a test for the `check_for_file_mentions` method, we will create a new test function in the `tests/test_coder.py` file. Here's the test function:

```python
tests/test_coder.py
<<<<<<< ORIGINAL
=======
import unittest
from unittest.mock import MagicMock
from aider.coder import Coder

class TestCoder(unittest.TestCase):
    def test_check_for_file_mentions(self):
        # Mock the IO object
        mock_io = MagicMock()
        mock_io.get_input.return_value = "Please check file1.txt and file2.py"
        mock_io.confirm_ask.return_value = True

        # Initialize the Coder object with the mocked IO
        coder = Coder(io=mock_io, openai_api_key="fake_key")

        # Add sample files to the Coder object
        coder.abs_fnames = {
            "/path/to/repo/file1.txt",
            "/path/to/repo/file2.py",
        }
        coder.root = "/path/to/repo"

        # Call the check_for_file_mentions method
        result = coder.check_for_file_mentions("Please check file1.txt and file2.py")

        # Check if the result is as expected
        self.assertEqual(result, "Added files: file1.txt, file2.py")

if __name__ == "__main__":
    unittest.main()
>>>>>>> UPDATED
```

This test function creates a `Coder` object with a mocked IO, adds sample files to the object, and then calls the `check_for_file_mentions` method with a sample input. It checks if the returned result is as expected.

tests/test_coder.py

@@ -0,0 +1,29 @@
+import unittest
+from unittest.mock import MagicMock
+from aider.coder import Coder
+
+class TestCoder(unittest.TestCase):
+    def test_check_for_file_mentions(self):
+        # Mock the IO object
+        mock_io = MagicMock()
+        mock_io.get_input.return_value = "Please check file1.txt and file2.py"
+        mock_io.confirm_ask.return_value = True
+
+        # Initialize the Coder object with the mocked IO
+        coder = Coder(io=mock_io, openai_api_key="fake_key")
+
+        # Add sample files to the Coder object
+        coder.abs_fnames = {
+            "/path/to/repo/file1.txt",
+            "/path/to/repo/file2.py",
+        }
+        coder.root = "/path/to/repo"
+
+        # Call the check_for_file_mentions method
+        result = coder.check_for_file_mentions("Please check file1.txt and file2.py")
+
+        # Check if the result is as expected
+        self.assertEqual(result, "Added files: file1.txt, file2.py")
+
+if __name__ == "__main__":
+    unittest.main()