test: add weekly date index test and extract _check_value() helper

tests/conftest.py

@@ -7,6 +7,24 @@
 
 import pandas as pd
 
+
+def _check_value(key, detected, expected, i):
+    """
+    Helper function to check a single value (start or end) against expected value.
+
+    Args:
+        key: The key name ('start' or 'end')
+        detected: The detected value
+        expected: The expected value
+        i: Segment index for error messages
+    """
+    if isinstance(detected, float):
+        assert round(detected, 6) == round(expected, 6), \
+            f"Segment {i}: Expected {key} '{expected}', got '{detected}'"
+    else:
+        assert detected == expected, \
+            f"Segment {i}: Expected {key} '{expected}', got '{detected}'"
+
 def assert_segments_match(detected_segments, expected_segments):
     """
     Helper function to validate that detected segments match expected segments.
@@ -38,19 +56,8 @@ def assert_segments_match(detected_segments, expected_segments):
         assert detected['direction'] == expected['direction'], \
             f"Segment {i}: Expected direction '{expected['direction']}', got '{detected['direction']}'"
 
-        if isinstance(detected['start'], float):
-            assert round(detected['start'], 6) == round(expected['start'], 6), \
-                f"Segment {i}: Expected start '{expected['start']}', got '{detected['start']}'"
-        else:
-            assert detected['start'] == expected['start'], \
-                f"Segment {i}: Expected start '{expected['start']}', got '{detected['start']}'"
-
-        if isinstance(detected['end'], float):
-            assert round(detected['end'], 6) == round(expected['end'], 6), \
-                f"Segment {i}: Expected end '{expected['end']}', got '{detected['end']}'"
-        else:
-            assert detected['end'] == expected['end'], \
-                f"Segment {i}: Expected end '{expected['end']}', got '{detected['end']}'"
+        _check_value('start', detected['start'], expected['start'], i)
+        _check_value('end', detected['end'], expected['end'], i)
 
 
 def assert_segments_in_a_haystack(detected_segments, expected_segments):

tests/test_non_dates.py

@@ -91,4 +91,33 @@ def test_string_index(self):
             {'direction': 'Flat', 'start': 'Step 168', 'end': 'Step 180'},
         ]
 
+        assert_segments_match(results.segments, expected_segments)
+
+    @pytest.mark.core
+    def test_weekly_date_index(self):
+        """Test standard gradual trend with weekly-spaced dates."""
+        df = pt.load_data('series_synthetic')
+        # Create weekly dates starting from 2026-01-01
+        df['weekly_date'] = pd.date_range(start='2026-01-01', periods=len(df), freq='W')
+        results = pt.detect_trends(
+            df,
+            value_col='gradual',
+            date_col='weekly_date',
+            plot=False,
+            method_params={'is_abrupt_padded': False}
+        )
+
+        # Expected segments based on current behavior
+        expected_segments = [
+            {'direction': 'Up',   'start': pd.Timestamp('2026-01-11'),  'end': pd.Timestamp('2026-06-14')},
+            {'direction': 'Down', 'start': pd.Timestamp('2026-06-21'),  'end': pd.Timestamp('2026-09-06')},
+            {'direction': 'Flat', 'start': pd.Timestamp('2026-09-13'),  'end': pd.Timestamp('2026-10-04')},
+            {'direction': 'Up',   'start': pd.Timestamp('2026-10-11'),  'end': pd.Timestamp('2027-05-23')},
+            {'direction': 'Flat', 'start': pd.Timestamp('2027-05-30'),  'end': pd.Timestamp('2027-06-13')},
+            {'direction': 'Down', 'start': pd.Timestamp('2027-06-20'),  'end': pd.Timestamp('2027-09-26')},
+            {'direction': 'Up',   'start': pd.Timestamp('2027-10-03'),  'end': pd.Timestamp('2028-06-11')},
+            {'direction': 'Down', 'start': pd.Timestamp('2028-06-18'),  'end': pd.Timestamp('2029-03-18')},
+            {'direction': 'Flat', 'start': pd.Timestamp('2029-03-25'),  'end': pd.Timestamp('2029-06-17')},
+        ]
+
         assert_segments_match(results.segments, expected_segments)