Add tests for changed code and region aware

gerrychain/constraints/__init__.py

@@ -45,7 +45,7 @@
                           no_worse_L_minus_1_polsby_popper)
 from .contiguity import (contiguous, contiguous_bfs, no_more_discontiguous,
                          single_flip_contiguous)
-from .validity import (Validator, districts_within_tolerance,
+from .validity import (Validator, deviation_from_ideal, districts_within_tolerance,
                        no_vanishing_districts, refuse_new_splits,
                        within_percent_of_ideal_population)
 
@@ -56,5 +56,5 @@
         "L_minus_1_polsby_popper", "no_worse_L1_reciprocal_polsby_popper",
         "no_worse_L_minus_1_polsby_popper", "contiguous", "contiguous_bfs",
         "no_more_discontiguous", "single_flip_contiguous", "Validator",
-        "districts_within_tolerance", "no_vanishing_districts",
+        "deviation_from_ideal", "districts_within_tolerance", "no_vanishing_districts",
         "refuse_new_splits", "within_percent_of_ideal_population", "Bounds"]

tests/constraints/test_validity.py

@@ -8,7 +8,8 @@
                                     contiguous, contiguous_bfs,
                                     districts_within_tolerance,
                                     no_vanishing_districts,
-                                    single_flip_contiguous)
+                                    single_flip_contiguous,
+                                    deviation_from_ideal)
 from gerrychain.partition import Partition
 from gerrychain.partition.partition import get_assignment
 from gerrychain.graph import Graph
@@ -173,3 +174,8 @@ def test_no_vanishing_districts_works():
     partition.assignment.update_flows({1: {"out": set(), "in": {2}}, 2: {"out": {2}, "in": set()}})
 
     assert not no_vanishing_districts(partition)
+
+def test_deviation_from_ideal():
+    mock_partition = {"population": {0: 99.0, 1: 101.0}}
+    assert deviation_from_ideal(mock_partition, "population") == \
+        {0: -0.01, 1: 0.01}