Update Voronoi tests.

src/Triangle.Tests/Helper.cs

@@ -45,8 +45,8 @@ public static Polygon SplitRectangle(double left, double top,
             poly.Add(new Contour(points, mark, true));
             poly.Add(new Segment(midTop, midBottom));
 
-            poly.Regions.Add(new RegionPointer(left + midX / 2, bottom + midY / 2, 1));
-            poly.Regions.Add(new RegionPointer(right - midX / 2, bottom + midY / 2, 2));
+            poly.Regions.Add(new RegionPointer(left + midX / 2, bottom + midY, 1));
+            poly.Regions.Add(new RegionPointer(right - midX / 2, bottom + midY, 2));
 
             return poly;
         }

src/Triangle.Tests/Voronoi/BoundedVoronoiTest.cs

@@ -28,6 +28,12 @@ public void TestBoundedVoronoi()
             // the Voronoi diagram.
             Assert.That(voronoi.Vertices.Count(v => v.Label == 0), Is.EqualTo(12));
             Assert.That(voronoi.Vertices.Count(v => v.ID >= mesh.Triangles.Count), Is.EqualTo(12));
+
+            // All Voronoi cells should have a generator vertex.
+            Assert.That(voronoi.Faces.All(f => f.Generator is not null));
+
+            // Check DCEL topology (all Voronoi cells should be closed).
+            Assert.That(voronoi.IsConsistent());
         }
     }
 }

src/Triangle.Tests/Voronoi/StandardVoronoiTest.cs

@@ -26,6 +26,12 @@ public void TestStandardVoronoi()
             // should have 6 infinite edges.
             Assert.That(voronoi.Vertices.Count(v => v.Label == 0), Is.EqualTo(6));
             Assert.That(voronoi.Vertices.Count(v => v.ID >= mesh.Triangles.Count), Is.EqualTo(6));
+
+            // All Voronoi cells should have a generator vertex.
+            Assert.That(voronoi.Faces.All(f => f.Generator is not null));
+
+            // Check DCEL topology (account for unbounded Voronoi cells).
+            Assert.That(voronoi.IsConsistent(false));
         }
     }
 }