--- a
+++ b/tests/test_preprocessing_utils.py
@@ -0,0 +1,68 @@
+import unittest
+from unittest.mock import patch, mock_open, MagicMock
+import xml.etree.ElementTree as ET
+import preprocessing_utils
+
+class TestExtractEligibilityCriteria(unittest.TestCase):
+    @patch('os.path.exists')
+    @patch('xml.etree.ElementTree.ElementTree')
+    @patch('xml.etree.ElementTree.fromstring')
+    @patch('builtins.open', new_callable=mock_open, read_data='<xml><eligibility><criteria><textblock>Test Criteria</textblock></criteria></eligibility></xml>')
+    def test_extract_eligibility_criteria(self, mock_file, mock_fromstring, mock_tree, mock_exists):
+        mock_exists.return_value = True
+        mock_tree_instance = mock_tree.return_value
+        mock_tree_instance.getroot.return_value.find.return_value.text.strip.return_value = 'Test Criteria'
+        
+        mock_trial_id = MagicMock()
+        mock_trial_id.__str__.return_value = 'test_trial_id'
+        
+        result = preprocessing_utils.extract_eligibility_criteria(mock_trial_id)
+        self.assertEqual(result, 'Test Criteria')
+
+    @patch('os.path.exists')
+    def test_extract_eligibility_criteria_file_not_found(self, mock_exists):
+        mock_exists.return_value = False
+        
+        result = preprocessing_utils.extract_eligibility_criteria('test_trial_id')
+        self.assertIsNone(result)
+
+    @patch('os.path.exists')
+    @patch('xml.etree.ElementTree.fromstring')
+    @patch('builtins.open', new_callable=mock_open, read_data='<xml><eligibility><criteria><textblock>Test Criteria</textblock></criteria></eligibility></xml>')
+    def test_extract_eligibility_criteria_parse_error(self, mock_file, mock_fromstring, mock_exists):
+        mock_exists.return_value = True
+        mock_fromstring.side_effect = ET.ParseError()
+        
+        result = preprocessing_utils.extract_eligibility_criteria('test_trial_id')
+        self.assertIsNone(result)
+        
+class TestSplitLineToSentences(unittest.TestCase):
+    @patch('preprocessing_utils.utils.replace_parentheses_with_braces')
+    def test_split_line_to_sentences(self, mock_replace):
+        mock_replace.return_value = '01.02.03.04 Some text here'
+        regex_patterns = ['^\\d{1,2}\\.\\d{1,2}\\.\\d{1,2}\\.\\d{1,2}']
+        exception_patterns = {}
+        
+        result = preprocessing_utils.split_by_leading_char_from_regex_patterns('01.02.03.04 Some text here', regex_patterns, exception_patterns)
+        self.assertEqual(result, ['01.02.03.04 Some text here'])
+
+    @patch('preprocessing_utils.utils.replace_parentheses_with_braces')
+    def test_split_line_to_sentences_with_exception(self, mock_replace):
+        mock_replace.return_value = '01.02.03 Some text here'
+        regex_patterns = ['^\\d{1,2}\\.\\d{1,2}\\.\\d{1,2}']
+        exception_patterns = {'03 Some': ''}
+        
+        result = preprocessing_utils.split_by_leading_char_from_regex_patterns('01.02.03 Some text here', regex_patterns, exception_patterns)
+        self.assertEqual(result, ['01.02.03 Some text here'])
+
+    @patch('preprocessing_utils.utils.replace_parentheses_with_braces')
+    def test_split_line_to_sentences_no_match(self, mock_replace):
+        mock_replace.return_value = 'No matching pattern here'
+        regex_patterns = ['^\\d{1,2}\\.\\d{1,2}\\.\\d{1,2}']
+        exception_patterns = {}
+        
+        result = preprocessing_utils.split_by_leading_char_from_regex_patterns('No matching pattern here', regex_patterns, exception_patterns)
+        self.assertEqual(result, ['No matching pattern here'])
+
+if __name__ == '__main__':
+    unittest.main()
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