diff --git a/services/analysis-engine/tests/test_sections_utils.py b/services/analysis-engine/tests/test_sections_utils.py
new file mode 100644
index 00000000..b33628ff
--- /dev/null
+++ b/services/analysis-engine/tests/test_sections_utils.py
@@ -0,0 +1,40 @@
+"""Tests for section utility functions."""
+
+import logging
+from unittest.mock import Mock
+
+import pytest
+
+from bandscope_analysis.sections.utils import validate_section
+
+
+@pytest.mark.parametrize(
+    ("section", "index", "expected_id"),
+    [
+        ({"id": "custom-id", "label": "intro"}, 1, "custom-id"),
+        ({"label": "intro"}, 2, "section-2"),
+    ],
+)
+def test_validate_section_accepts_dict_sections(
+    section: dict[str, str], index: int, expected_id: str
+) -> None:
+    """Verify valid section dictionaries return stable ids without warnings."""
+    mock_logger = Mock(spec=logging.Logger)
+
+    result = validate_section(section, index=index, logger=mock_logger)
+
+    assert result == expected_id
+    mock_logger.warning.assert_not_called()
+
+
+def test_validate_section_warns_for_invalid_section_type() -> None:
+    """Verify invalid sections log type context and return a generated id."""
+    mock_logger = Mock(spec=logging.Logger)
+
+    result = validate_section(["intro"], index=3, logger=mock_logger)
+
+    assert result == "section-3"
+    mock_logger.warning.assert_called_once()
+    warning_context = " ".join(str(value) for value in mock_logger.warning.call_args.args)
+    assert "3" in warning_context
+    assert "list" in warning_context
diff --git a/services/analysis-engine/tests/test_segmenter.py b/services/analysis-engine/tests/test_segmenter.py
index 37fee9f9..f0284b30 100644
--- a/services/analysis-engine/tests/test_segmenter.py
+++ b/services/analysis-engine/tests/test_segmenter.py
@@ -324,3 +324,75 @@ def test_segment_with_boundaries_handles_empty_short_and_failed_inputs() -> None
 
     assert "bad combined boundary" in failed_sections[0]["confidence_notes"]
     assert failed_boundaries == [(0.0, 20.0)]
+
+
+def test_detect_boundaries_ignores_peak_indexes_without_frame_times() -> None:
+    """Ensure peaks beyond frame_times length are skipped."""
+    novelty = np.array([0.0, 0.1, 0.2, 0.9, 0.2, 0.1, 0.0], dtype=np.float64)
+    frame_times = np.array([0.0, 1.0], dtype=np.float64)
+
+    boundaries = detect_boundaries(novelty, frame_times, 10.0)
+
+    assert boundaries == [0.0]
+
+
+def test_detect_boundaries_ignores_peaks_near_end_of_duration() -> None:
+    """Ensure boundaries are not created within one second of total duration."""
+    novelty = np.array([0.0, 0.1, 0.9, 0.1, 0.9, 0.1, 0.0], dtype=np.float64)
+    frame_times = np.array([0.0, 2.5, 5.0, 7.5, 9.5, 10.0, 10.5], dtype=np.float64)
+
+    boundaries = detect_boundaries(novelty, frame_times, 10.0)
+
+    assert boundaries == [0.0, 5.0]
+
+
+def test_detect_boundaries_threshold_floor_filters_small_peaks() -> None:
+    """Ensure the adaptive threshold floor suppresses tiny local maxima."""
+    novelty = np.array([0.0, 0.01, 0.09, 0.01, 0.0], dtype=np.float64)
+    frame_times = np.array([0.0, 1.0, 2.0, 3.0, 4.0], dtype=np.float64)
+
+    boundaries = detect_boundaries(novelty, frame_times, 10.0)
+
+    assert boundaries == [0.0]
+
+
+def test_detect_boundaries_flat_novelty_returns_start_only() -> None:
+    """Ensure flat novelty does not produce boundaries."""
+    novelty = np.ones(10, dtype=np.float64) * 0.5
+    frame_times = np.arange(10, dtype=np.float64)
+
+    boundaries = detect_boundaries(novelty, frame_times, 10.0)
+
+    assert boundaries == [0.0]
+
+
+def test_detect_boundaries_skips_candidates_too_close_to_previous_boundary() -> None:
+    """Ensure candidate boundaries must satisfy the minimum segment length."""
+    novelty = np.array([0.0, 0.9, 0.0, 0.9, 0.0], dtype=np.float64)
+    frame_times = np.array([0.0, 1.0, 3.0, 5.0, 7.0], dtype=np.float64)
+
+    boundaries = detect_boundaries(novelty, frame_times, 10.0, min_segment_seconds=4.0)
+
+    assert boundaries == [0.0, 5.0]
+
+
+def test_detect_boundaries_truncates_to_unique_increasing_boundaries() -> None:
+    """Ensure truncation preserves ordered unique boundary times."""
+    novelty = np.tile(np.array([0.0, 1.0, 0.0], dtype=np.float64), 60)
+    frame_times = np.arange(len(novelty), dtype=np.float64)
+
+    boundaries = detect_boundaries(novelty, frame_times, 200.0, min_segment_seconds=1.0)
+
+    assert len(boundaries) == 20
+    assert boundaries == sorted(set(boundaries))
+    assert all(boundaries[index] < boundaries[index + 1] for index in range(len(boundaries) - 1))
+
+
+def test_detect_boundaries_accepts_right_edge_peak_when_not_near_duration_end() -> None:
+    """Ensure the last novelty frame can be used as a boundary."""
+    novelty = np.array([0.0, 0.1, 0.1, 0.1, 0.9], dtype=np.float64)
+    frame_times = np.array([0.0, 1.0, 2.0, 3.0, 4.0], dtype=np.float64)
+
+    boundaries = detect_boundaries(novelty, frame_times, 10.0, min_segment_seconds=2.0)
+
+    assert boundaries == [0.0, 4.0]