added linear slider

server/tests/test_elevation.py

@@ -141,6 +141,22 @@ def test_build_elevation_grid_delta(monkeypatch):
     assert all("delta_m" in p for p in result["points"])
 
 
+def test_build_elevation_grid_fine_step_small_radius(monkeypatch):
+    monkeypatch.setattr(elev, "_probe_checked_at", 0.0)
+    monkeypatch.setattr(elev, "probe_elevation_api", lambda force=False: {"ok": True, "error": None})
+    monkeypatch.setattr(elev, "fetch_elevation_m", lambda lat, lon: 120.0)
+    monkeypatch.setattr(
+        elev,
+        "fetch_elevations_batch",
+        lambda lats, lons: [120.0 + i * 0.1 for i in range(len(lats))],
+    )
+
+    result = elev.build_elevation_grid(55.75, 37.62, radius_m=50, step_m=1)
+    assert result["ok"] is True
+    assert result["step_m"] == 1
+    assert len(result["points"]) > 1000
+
+
 def test_build_elevation_grid_limits_points(monkeypatch):
     monkeypatch.setattr(elev, "_probe_checked_at", 0.0)
     monkeypatch.setattr(elev, "probe_elevation_api", lambda force=False: {"ok": True, "error": None})