fix: make stratigraphic order consistent between methods and add unit test (#320)

* ci: pin map2loop/visualisation release-please versions to fix bad auto-bump

Neither package has a component-scoped release-please tag yet (they
were only just added to the workspace in #301/#302), so release-please
had no correct anchor for their next version and fell back to
misreading one of the repo's old generic v1.6.5 LoopStructural tags as
their baseline, proposing 1.6.5 for both in the open release PR
instead of a proper minor bump from their real current versions
(map2loop 3.3.1, loopstructuralvisualisation 0.1.17). One-time
release-as pins to the correct next versions; remove once that
release PR has merged and each package has its own release-please tag
to anchor future bumps.

* fix: ensuring stratigraphic order is consistent between methods + adding test

Author: lachlangrose

LoopStructural/modelling/core/stratigraphic_column.py

@@ -668,7 +668,7 @@ def get_isovalues(self) -> dict[str, float]:
         surface_values = {}
         for g in reversed(self.get_groups()):
             v = 0
-            for u in g.units:
+            for u in reversed(g.units):
                 surface_values[u.name] = {'value':v,'group':g.name,'colour':u.colour}
                 v += u.thickness
         return surface_values

tests/unit/modelling/test_stratigraphic_column.py

@@ -430,6 +430,20 @@ def test_get_isovalues(self):
         assert isovalues["B"]["value"] == 0
         assert isovalues["B"]["group"] == "Group_0"
 
+    def test_get_isovalues_multi_unit_group(self):
+        # Isovalues must match update_unit_values: the base of the oldest
+        # unit in a group is 0, and each unit's thickness gives the base
+        # value of the next (younger) unit.
+        column = StratigraphicColumn()
+        column.clear(basement=False)
+        column.add_unit("A", thickness=10, id=0)
+        column.add_unit("B", thickness=5, id=1)
+        column.add_unit("C", thickness=3, id=2)
+        isovalues = column.get_isovalues()
+        assert isovalues["A"]["value"] == 0
+        assert isovalues["B"]["value"] == 10
+        assert isovalues["C"]["value"] == 15
+
 
 class TestOrderingAndUpdates:
     def test_update_order_reorders_elements(self):