fixed calibration data not loading due to path

tests/test_calibration.py

@@ -243,8 +243,84 @@ def test_missing_cal_path_raises():
 
 def test_parse_shipped_box_file_directly():
     cal = parse(json.loads(_box_cal_path().read_text(encoding="utf-8")), source_path=_box_cal_path())
-    assert cal.schema_version == 1
+    assert cal.schema_version == 2
     assert cal.convert(10000.0, 36000.0, -36000.0) == pytest.approx((0.377, 1.19, -1.19))
+    # The shipped file names both shear axes outright: no shared block, no clone.
+    assert set(cal.channels) == {"fn", "fx", "fy"}
+    fx, fy = cal.get("FX"), cal.get("FY")
+    assert fx is not None and fy is not None and fx is not fy
+    for curve in (fx, fy):
+        assert curve.signed is True
+        assert curve.extrapolate is True
+        assert curve.clamp_output_min == pytest.approx(0.0)
+        assert len(curve.points) == 3
+    assert fx.raw_key == "fshearx"
+    assert fy.raw_key == "fsheary"
+
+
+def test_the_shipped_box_shear_axes_can_drift_apart(tmp_path: Path):
+    """The whole point of the split: FX and FY are independent curves.
+
+    A document with the same shape as the shipped one but different per-axis
+    points must apply each axis's own curve. Re-collapsing the axes into one
+    shared ``shear`` block makes this fail.
+    """
+    doc = {
+        "schema_version": 2,
+        "unit": "N",
+        "channels": {
+            "normal": {
+                "method": "piecewise_linear",
+                "points": [[0.0, 0.0], [1000.0, 1.0]],
+            },
+            "shear_x": {
+                "method": "piecewise_linear",
+                "signed": True,
+                "input": "components",
+                "extrapolate": True,
+                "clamp_output_min": 0.0,
+                "points": [[0.0, 0.0], [500.0, 2.0]],
+            },
+            "shear_y": {
+                "method": "piecewise_linear",
+                "signed": True,
+                "input": "components",
+                "extrapolate": True,
+                "clamp_output_min": 0.0,
+                "points": [[0.0, 0.0], [500.0, 3.0]],
+            },
+        },
+    }
+    path = tmp_path / "split.json"
+    path.write_text(json.dumps(doc), encoding="utf-8")
+    cal = load(path)
+    assert cal is not None
+    assert cal.convert(0.0, 500.0, 500.0)[1:] == pytest.approx((2.0, 3.0))
+    assert cal.convert(0.0, -500.0, 500.0)[1:] == pytest.approx((-2.0, 3.0))
+
+
+def test_out_of_range_readings_extend_instead_of_being_dropped():
+    """Outside the calibrated range the nearest segment is extended.
+
+    This pins the "extend, never ignore, never reuse a previous coefficient"
+    behaviour of the shipped box file, so flipping ``extrapolate`` has to be a
+    deliberate edit that fails this test first.
+    """
+    cal = load(sensor_type="box")
+    assert cal is not None
+    fx, fy, fn = cal.get("FX"), cal.get("FY"), cal.get("FN")
+    assert fx is not None and fy is not None and fn is not None
+    # 136000 = 2 x the top raw break (68000 -> 2.06): the last segment's slope is
+    # applied again, so the value keeps growing past the calibrated range.
+    (r0, n0), (r1, n1) = fx.points[-2], fx.points[-1]
+    extended = n1 + (n1 - n0) / (r1 - r0) * (136000.0 - r1)
+    assert extended > n1
+    assert fx.convert_component(136000.0) == pytest.approx(extended)
+    assert fy.convert_component(136000.0) == pytest.approx(extended)
+    # A negative beyond the range keeps its sign.
+    assert fx.convert_component(-136000.0) == pytest.approx(-extended)
+    # Below the first point the normal channel floors at clamp_output_min.
+    assert fn.convert(500.0) == pytest.approx(0.0)
 
 
 # ------------------------------------------------------- filter fingerprint