tweaks

test/geometry_test.rb

@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+class GeometryTest < Minitest::Test
+  def setup
+    @data = MoonModel::DataSet.new
+  end
+
+  def test_solid_one_piece_is_a_closed_outer_volume_without_inner_surface
+    solid = structure("solid")
+    hollow = structure("hollow")
+
+    assert solid.valid?
+    assert_manifold solid
+    assert_equal hollow.triangles.length / 2, solid.triangles.length
+    assert_equal hollow.vertices.length / 2, solid.vertices.length
+  end
+
+  def test_solid_single_color_grid_remains_manifold
+    config = config_for("solid", "grid" => { "enabled" => true, "depth_mm" => 0.4 })
+    mesh = MoonModel::Geometry.build(config, @data).parts.first[:meshes].first
+
+    assert mesh.valid?
+    assert_manifold mesh
+  end
+
+  def test_segmented_output_is_hollow_even_when_solid_is_requested
+    config = config_for("solid", "purpose" => "box", "assembly" => "eight_piece")
+    result = MoonModel::Geometry.build(config, @data)
+
+    assert result.segmented?
+    assert_equal "hollow", result.statistics["interior"]
+  end
+
+  private
+
+  def structure(interior)
+    MoonModel::Geometry.build(config_for(interior), @data).parts.first[:meshes].first
+  end
+
+  def config_for(interior, extra = {})
+    MoonModel::Config.new({
+      "size" => { "value" => 40 },
+      "shell" => { "interior" => interior },
+      "resolution" => { "longitude_segments" => 24 }
+    }.merge(extra))
+  end
+
+  def assert_manifold(mesh)
+    edge_uses = Hash.new(0)
+    mesh.triangles.each do |triangle|
+      triangle.each_index do |index|
+        edge_uses[[triangle[index], triangle[(index + 1) % 3]].sort] += 1
+      end
+    end
+    assert edge_uses.values.all? { |count| count == 2 }, "every edge must belong to exactly two faces"
+  end
+end