feat(api): allow setting a fixed override to '..byVolume' properties

api/src/opentrons/protocol_api/_liquid_properties.py

@@ -62,6 +62,11 @@ def get_for_volume(self, volume: float) -> float:
                 interp(validated_volume, self._sorted_volumes, self._sorted_values)
             )
 
+    def set_for_all_volumes(self, value: float) -> None:
+        """Override all existing volume-dependent values with the given value."""
+        self.clear_values()
+        self.set_for_volume(0, value)
+
     def set_for_volume(self, volume: float, value: float) -> None:
         """Add a new volume and value for the property for the interpolation curve."""
         validated_volume = validation.ensure_positive_float(volume)

api/tests/opentrons/protocol_api/test_liquid_class_properties.py

@@ -453,6 +453,22 @@ def test_liquid_handling_property_by_volume() -> None:
     assert subject.get_for_volume(1) == 50.0
     assert subject.get_for_volume(1000) == 250.0
 
+    # Test fixed overrides
+    subject.set_for_all_volumes(4321)
+    for volume in (0, 1, 7, 100):
+        assert subject.get_for_volume(volume) == 4321
+
+    # Test resetting to default
+    subject.reset_values()
+    assert subject.as_dict() == {5.0: 50, 10.0: 250}
+    assert subject.get_for_volume(7) == 130.0
+
+    # Test clearing all values
+    subject.clear_values()
+    assert subject.as_dict() == {}
+    with pytest.raises(ValueError, match="No properties found for any volumes"):
+        subject.get_for_volume(7)
+
 
 def test_non_existent_property_raises_error() -> None:
     """It should raise an attribute error if the set property does not exist."""