Initial MoonModel implementation

test/color_test.rb

@@ -0,0 +1,12 @@
+# frozen_string_literal: true
+
+require "test_helper"
+
+class ColorTest < Minitest::Test
+  def test_orders_by_luminance_and_is_deterministic
+    palette = [{ "name" => "white", "hex" => "#FFFFFF" }, { "name" => "black", "hex" => "#000000" }]
+    ordered = MoonModel::Color.ordered_palette(palette)
+    assert_equal %w[black white], ordered.map { |c| c["name"] }
+    assert_equal MoonModel::Color.choose(0.4, ordered, 10, 11), MoonModel::Color.choose(0.4, ordered, 10, 11)
+  end
+end