diff --git a/tests/basic/test_linter.py b/tests/basic/test_linter.py
index e69de29bb..055cdb7d5 100644
--- a/tests/basic/test_linter.py
+++ b/tests/basic/test_linter.py
@@ -0,0 +1,62 @@
+import unittest
+from unittest.mock import patch, MagicMock
+from pathlib import Path
+from aider.linter import Linter
+
+class TestLinter(unittest.TestCase):
+    def setUp(self):
+        self.linter = Linter(encoding="utf-8", root="/test/root")
+
+    def test_init(self):
+        self.assertEqual(self.linter.encoding, "utf-8")
+        self.assertEqual(self.linter.root, "/test/root")
+        self.assertIn("python", self.linter.languages)
+
+    @patch('pathlib.Path.is_file')
+    def test_check_eslint_unix(self, mock_is_file):
+        mock_is_file.return_value = True
+        self.linter._check_eslint()
+        self.assertIn("typescript", self.linter.languages)
+        self.assertTrue(self.linter.languages["typescript"].startswith('"'))
+        self.assertTrue(self.linter.languages["typescript"].endswith('" --format unix'))
+
+    @patch('pathlib.Path.is_file')
+    def test_check_eslint_windows(self, mock_is_file):
+        def side_effect(path):
+            return str(path).endswith('eslint.cmd')
+        mock_is_file.side_effect = side_effect
+        self.linter._check_eslint()
+        self.assertIn("typescript", self.linter.languages)
+        self.assertTrue(self.linter.languages["typescript"].endswith('eslint.cmd" --format unix'))
+
+    def test_set_linter(self):
+        self.linter.set_linter("javascript", "eslint")
+        self.assertEqual(self.linter.languages["javascript"], "eslint")
+
+    def test_get_rel_fname(self):
+        self.assertEqual(self.linter.get_rel_fname("/test/root/file.py"), "file.py")
+        self.assertEqual(self.linter.get_rel_fname("/other/path/file.py"), "/other/path/file.py")
+
+    @patch('subprocess.Popen')
+    def test_run_cmd(self, mock_popen):
+        mock_process = MagicMock()
+        mock_process.returncode = 0
+        mock_process.communicate.return_value = ("", None)
+        mock_popen.return_value = mock_process
+
+        result = self.linter.run_cmd("test_cmd", "test_file.py", "code")
+        self.assertIsNone(result)
+
+    @patch('subprocess.Popen')
+    def test_run_cmd_with_errors(self, mock_popen):
+        mock_process = MagicMock()
+        mock_process.returncode = 1
+        mock_process.communicate.return_value = ("Error message", None)
+        mock_popen.return_value = mock_process
+
+        result = self.linter.run_cmd("test_cmd", "test_file.py", "code")
+        self.assertIsNotNone(result)
+        self.assertIn("Error message", result.text)
+
+if __name__ == '__main__':
+    unittest.main()