test: add unit tests for parsing functions, logger, and utility

Add 34 tests across 3 test files:

- test_browser_agent_parsing.py (20 tests): expand existing tests with
  coverage for extract_links, extract_form, clean_links, parse_answer,
  select_link, jsonify_search_results, stringify_search_results, and
  select_unvisited
- test_logger.py (9 tests): Logger initialization, message writing, log
  level handling, deduplication, and folder creation
- test_utility.py (5 tests): get_color_map returns correct structure and
  color values

All tests avoid LLM requests per issue requirements.

tests/test_logger.py

@@ -0,0 +1,92 @@
+import unittest
+import os
+import sys
+import shutil
+import logging
+sys.path.insert(0, os.path.abspath(os.path.join(os.path.dirname(__file__), '..')))
+
+from sources.logger import Logger
+
+
+class TestLogger(unittest.TestCase):
+    """Test suite for the Logger class."""
+
+    def setUp(self):
+        self.logger = Logger("test_logger.log")
+
+    def tearDown(self):
+        if os.path.exists('.logs'):
+            for handler in self.logger.logger.handlers[:]:
+                handler.close()
+                self.logger.logger.removeHandler(handler)
+            log_path = os.path.join('.logs', 'test_logger.log')
+            if os.path.exists(log_path):
+                os.remove(log_path)
+
+    def test_initialization(self):
+        """Test logger initializes correctly."""
+        self.assertTrue(self.logger.enabled)
+        self.assertIsNotNone(self.logger.logger)
+        self.assertTrue(os.path.exists('.logs'))
+
+    def test_log_creates_file(self):
+        """Test that logging creates a log file."""
+        self.logger.info("test message")
+        self.assertTrue(os.path.exists(self.logger.log_path))
+
+    def test_log_writes_message(self):
+        """Test that log messages are written to file."""
+        self.logger.info("hello world")
+        with open(self.logger.log_path, 'r') as f:
+            content = f.read()
+        self.assertIn("hello world", content)
+
+    def test_log_deduplication(self):
+        """Test that consecutive identical messages are not duplicated."""
+        self.logger.info("duplicate message")
+        self.logger.info("duplicate message")
+        with open(self.logger.log_path, 'r') as f:
+            content = f.read()
+        self.assertEqual(content.count("duplicate message"), 1)
+
+    def test_log_different_messages(self):
+        """Test that different messages are all written."""
+        self.logger.info("message one")
+        self.logger.info("message two")
+        with open(self.logger.log_path, 'r') as f:
+            content = f.read()
+        self.assertIn("message one", content)
+        self.assertIn("message two", content)
+
+    def test_error_level(self):
+        """Test error level logging."""
+        self.logger.error("error occurred")
+        with open(self.logger.log_path, 'r') as f:
+            content = f.read()
+        self.assertIn("ERROR", content)
+        self.assertIn("error occurred", content)
+
+    def test_warning_level(self):
+        """Test warning level logging."""
+        self.logger.warning("warning issued")
+        with open(self.logger.log_path, 'r') as f:
+            content = f.read()
+        self.assertIn("WARNING", content)
+        self.assertIn("warning issued", content)
+
+    def test_create_folder(self):
+        """Test folder creation."""
+        test_path = ".test_log_folder"
+        result = self.logger.create_folder(test_path)
+        self.assertTrue(result)
+        self.assertTrue(os.path.exists(test_path))
+        os.rmdir(test_path)
+
+    def test_create_folder_already_exists(self):
+        """Test folder creation when folder already exists."""
+        result = self.logger.create_folder('.logs')
+        self.assertTrue(result)
+
+
+if __name__ == '__main__':
+    unittest.main()