add tests: test_metrics.py (31 tests) — _haversine_m correctness and symmetry; compute() end-to-end for GPS distance, device distance preference, moving-time stop exclusion, elevation gain/loss,

HR, power, bbox, endpoints; MMP sliding-window constant and peak cases; _fastest_time_for_distance and compute_best_efforts for running targets; _best_climb including gap-reset
  behaviour.

  test_dedup.py (20 tests) — Exact hash lookup; near-duplicate thresholds at the ±5 min / ±5% edges; skipping already-marked duplicates; zero/null distance guard; pick_canonical source
  quality ranking; full save/reload round-trip including duplicate_of persistence.

  test_simplify.py (19 tests) — RDP mask collinear removal, corner retention, epsilon=0 keeps all; simplify_track with GPS and no-GPS input; preview_coords max-points cap and [lat, lon]
  format; build_geojson structure, coordinate order ([lon, lat, ele]), speeds parallel array, point counts.

  test_db.py (35 tests) — WAL mode, idempotent schema; user CRUD and bcrypt authenticate; session creation, lookup, expiry and auto-delete, purge; invite create/use/limit (admin
  unlimited, regular capped at 3); cascade delete of sessions when user is deleted.

tests/test_simplify.py

@@ -0,0 +1,212 @@
+"""Tests for bincio.extract.simplify."""
+
+from datetime import datetime, timezone
+
+import pytest
+
+from bincio.extract.models import DataPoint
+from bincio.extract.simplify import (
+    _rdp_mask,
+    build_geojson,
+    preview_coords,
+    simplify_track,
+)
+
+
+# ── Helpers ───────────────────────────────────────────────────────────────────
+
+def _ts(i: int = 0) -> datetime:
+    from datetime import timedelta
+    return datetime(2024, 1, 1, 0, 0, 0, tzinfo=timezone.utc) + timedelta(seconds=i)
+
+
+def _pt(lat: float, lon: float, ele: float | None = None, spd: float | None = None, i: int = 0) -> DataPoint:
+    return DataPoint(timestamp=_ts(i), lat=lat, lon=lon, elevation_m=ele, speed_kmh=spd)
+
+
+def _pts_no_gps(n: int) -> list[DataPoint]:
+    return [DataPoint(timestamp=_ts(i)) for i in range(n)]
+
+
+# ── _rdp_mask ─────────────────────────────────────────────────────────────────
+
+def test_rdp_mask_collinear_removes_middle():
+    # Three collinear points — the middle one should be dropped
+    coords = [[0.0, 0.0], [0.5, 0.0], [1.0, 0.0]]
+    mask = _rdp_mask(coords, epsilon=0.001)
+    assert mask[0] is True
+    assert mask[1] is False   # middle collinear point removed
+    assert mask[2] is True
+
+
+def test_rdp_mask_always_keeps_endpoints():
+    coords = [[0.0, 0.0], [0.5, 1.0], [1.0, 0.0]]
+    mask = _rdp_mask(coords, epsilon=0.001)
+    assert mask[0] is True
+    assert mask[-1] is True
+
+
+def test_rdp_mask_large_deviation_kept():
+    # Middle point is far off the line — must be kept
+    coords = [[0.0, 0.0], [0.5, 1.0], [1.0, 0.0]]
+    mask = _rdp_mask(coords, epsilon=0.001)
+    assert mask[1] is True
+
+
+def test_rdp_mask_single_point():
+    mask = _rdp_mask([[0.0, 0.0]], epsilon=0.001)
+    assert mask == [True]
+
+
+def test_rdp_mask_two_points():
+    mask = _rdp_mask([[0.0, 0.0], [1.0, 1.0]], epsilon=0.001)
+    assert mask == [True, True]
+
+
+def test_rdp_mask_epsilon_zero_keeps_all():
+    coords = [[float(i), 0.0] for i in range(5)]
+    mask = _rdp_mask(coords, epsilon=0.0)
+    assert all(mask)
+
+
+# ── simplify_track ────────────────────────────────────────────────────────────
+
+def test_simplify_track_collinear_removes_interior():
+    # Straight line — only endpoints should survive with epsilon > 0
+    pts = [_pt(48.0 + i * 0.001, 11.0, i=i) for i in range(5)]
+    result = simplify_track(pts, epsilon=0.0001)
+    # Endpoints always kept; interior collinear points dropped
+    assert result[0].lat == pytest.approx(48.0)
+    assert result[-1].lat == pytest.approx(48.004)
+    assert len(result) < len(pts)
+
+
+def test_simplify_track_corner_kept():
+    # L-shaped route — the corner must survive
+    pts = [
+        _pt(48.000, 11.000, i=0),
+        _pt(48.001, 11.000, i=1),  # going north
+        _pt(48.002, 11.000, i=2),
+        _pt(48.002, 11.001, i=3),  # turn east — this is the corner
+        _pt(48.002, 11.002, i=4),
+    ]
+    result = simplify_track(pts, epsilon=0.0001)
+    latlons = [(p.lat, p.lon) for p in result]
+    assert (48.002, 11.000) in latlons   # corner kept
+
+
+def test_simplify_track_no_gps_points():
+    pts = _pts_no_gps(10)
+    result = simplify_track(pts)
+    assert result == []
+
+
+def test_simplify_track_single_gps_point():
+    pts = [_pt(48.0, 11.0)]
+    result = simplify_track(pts)
+    assert len(result) == 1
+
+
+def test_simplify_track_preserves_data_point_fields():
+    pts = [
+        _pt(48.0, 11.0, ele=100.0, spd=20.0, i=0),
+        _pt(48.0, 12.0, ele=200.0, spd=30.0, i=1),
+    ]
+    result = simplify_track(pts)
+    assert result[0].elevation_m == 100.0
+    assert result[0].speed_kmh == 20.0
+
+
+# ── preview_coords ────────────────────────────────────────────────────────────
+
+def test_preview_coords_none_on_no_gps():
+    result = preview_coords(_pts_no_gps(10))
+    assert result is None
+
+
+def test_preview_coords_single_point_none():
+    result = preview_coords([_pt(48.0, 11.0)])
+    assert result is None
+
+
+def test_preview_coords_respects_max_points():
+    pts = [_pt(48.0 + i * 0.001, 11.0, i=i) for i in range(100)]
+    result = preview_coords(pts, max_points=10)
+    assert result is not None
+    assert len(result) <= 10
+
+
+def test_preview_coords_format():
+    pts = [_pt(48.123456789, 11.987654321, i=0), _pt(48.2, 12.0, i=1)]
+    result = preview_coords(pts)
+    assert result is not None
+    for coord in result:
+        assert len(coord) == 2
+        # Rounded to 5 decimal places
+        assert coord[0] == round(coord[0], 5)
+        assert coord[1] == round(coord[1], 5)
+
+
+def test_preview_coords_few_points_returned_all():
+    pts = [_pt(48.0, 11.0, i=0), _pt(48.1, 11.1, i=1), _pt(48.2, 11.2, i=2)]
+    result = preview_coords(pts, max_points=20)
+    assert result is not None
+    assert len(result) >= 2
+
+
+# ── build_geojson ─────────────────────────────────────────────────────────────
+
+def test_build_geojson_structure():
+    pts = [_pt(48.0, 11.0, ele=100.0, spd=20.0, i=i) for i in range(3)]
+    gj = build_geojson(pts, activity_id="test-123")
+    assert gj["type"] == "Feature"
+    assert gj["geometry"]["type"] == "LineString"
+    assert "coordinates" in gj["geometry"]
+    assert "properties" in gj
+    props = gj["properties"]
+    assert props["id"] == "test-123"
+    assert props["simplification"] == "rdp"
+    assert "speeds" in props
+    assert "point_count_simplified" in props
+
+
+def test_build_geojson_coordinates_order():
+    # GeoJSON uses [lon, lat, ele]
+    pts = [_pt(48.0, 11.0, ele=100.0, i=0), _pt(48.5, 11.5, ele=200.0, i=1)]
+    gj = build_geojson(pts, "act")
+    coords = gj["geometry"]["coordinates"]
+    assert len(coords) == 2
+    # First coord: lon=11.0, lat=48.0, ele=100.0
+    assert coords[0] == [11.0, 48.0, 100.0]
+
+
+def test_build_geojson_no_elevation_omits_z():
+    pts = [_pt(48.0, 11.0, ele=None, i=0), _pt(48.5, 11.5, ele=None, i=1)]
+    gj = build_geojson(pts, "act")
+    coords = gj["geometry"]["coordinates"]
+    for c in coords:
+        assert len(c) == 2   # no Z
+
+
+def test_build_geojson_speeds_parallel():
+    pts = [
+        _pt(48.0, 11.0, spd=10.0, i=0),
+        _pt(48.5, 11.5, spd=None, i=1),
+        _pt(49.0, 12.0, spd=20.0, i=2),
+    ]
+    gj = build_geojson(pts, "act")
+    speeds = gj["properties"]["speeds"]
+    coords = gj["geometry"]["coordinates"]
+    assert len(speeds) == len(coords)
+
+
+def test_build_geojson_point_counts():
+    pts = [_pt(48.0 + i * 0.001, 11.0, i=i) for i in range(10)]
+    gj = build_geojson(pts, "act", original_count=100)
+    assert gj["properties"]["point_count_original"] == 100
+    assert gj["properties"]["point_count_simplified"] <= 10
+
+
+def test_build_geojson_no_gps_points():
+    gj = build_geojson(_pts_no_gps(5), "act")
+    assert gj["geometry"]["coordinates"] == []