# Context:
USER: add a test for NO_COLOR
ASSISTANT: To add a test for the `NO_COLOR` environment variable, we will create a new test function in the `tests/test_io.py` file. Since this file does not exist, we will create it first.
```python
tests/test_io.py
<<<<<<< ORIGINAL
=======
import os
import unittest
from unittest.mock import patch
from aider.io import InputOutput
class TestInputOutput(unittest.TestCase):
def test_no_color_environment_variable(self):
with patch.dict(os.environ, {"NO_COLOR": "1"}):
io = InputOutput()
self.assertFalse(io.pretty)
if __name__ == "__main__":
unittest.main()
>>>>>>> UPDATED
```
This test function checks if the `pretty` attribute of the `InputOutput` class is set to `False` when the `NO_COLOR` environment variable is set.
