Add tests for edge collapsing

test/simplification_test.py

@@ -1,6 +1,13 @@
 import pytest
 import numpy as np
 from zmsh.simplification import compute_plane
+from zmsh.polytopal import (
+    standard_simplex,
+    join_vertices,
+    edge_collapse,
+    from_simplicial,
+    to_simplicial,
+)
 
 
 @pytest.mark.parametrize("dimension", [2, 3, 4])
@@ -15,3 +22,63 @@ def test_computing_planes(dimension):
             ts /= np.sum(ts)
             w = ts @ xs
             assert np.abs(p[0] + np.dot(p[1:], w)) < 1e-6
+
+
+def test_edge_collapse():
+    D_0 = np.ones((1, 5), dtype=np.int8)
+
+    D_1 = np.array(
+        [
+            [0, 0, 0, 0, -1, -1, -1, -1],
+            [-1, 0, 0, +1, +1, 0, 0, 0],
+            [+1, -1, 0, 0, 0, +1, 0, 0],
+            [0, +1, -1, 0, 0, 0, +1, 0],
+            [0, 0, +1, -1, 0, 0, 0, +1],
+        ],
+        dtype=np.int8,
+    )
+
+    D_2 = np.array(
+        [
+            [+1, 0, 0, 0],
+            [0, +1, 0, 0],
+            [0, 0, +1, 0],
+            [0, 0, 0, +1],
+            [+1, 0, 0, -1],
+            [-1, +1, 0, 0],
+            [0, -1, +1, 0],
+            [0, 0, -1, +1],
+        ],
+        dtype=np.int8,
+    )
+
+    Ds = [D_0, D_1, D_2]
+    vertex_ids = [1, 2]
+    Es = edge_collapse(Ds, vertex_ids)
+    simplices = to_simplicial(Es)
+    assert (vertex_ids[0] in simplices) and not (vertex_ids[1] in simplices)
+
+
+def test_bunny_collapse():
+    patch = np.array(
+        [
+            [3, 5, 1],
+            [7, 5, 8],
+            [3, 8, 5],
+            [5, 7, 4],
+            [5, 4, 9],
+            [7, 3, 2],
+            [8, 3, 7],
+            [5, 9, 0],
+            [3, 1, 10],
+            [6, 3, 10],
+            [0, 1, 5],
+            [2, 3, 6],
+        ],
+    )
+
+    Ds = from_simplicial(patch)
+    vertex_ids = [3, 5]
+    Es = edge_collapse(Ds, vertex_ids)
+    new_patch = to_simplicial(Es)
+    assert (vertex_ids[0] in new_patch) and not (vertex_ids[1] in new_patch)