Initial MoonModel implementation

test/test_helper.rb

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+# frozen_string_literal: true
+
+require "minitest/autorun"
+require "tmpdir"
+require "zip"
+require "moon_model"
+
+module TestData
+  def make_data(path, width: 16, height: 8)
+    elevations = Array.new(width * height) { |i| ((i % width) - width / 2) * 20 }
+    reflectance = Array.new(width * height) { |i| (255.0 * (i % width) / (width - 1)).round }
+    header = { "format_version" => 1, "title" => "test data", "width" => width, "height" => height,
+               "elevation_offset_range_m" => elevations.minmax }
+    encoded = JSON.generate(header)
+    Zlib::GzipWriter.open(path) do |gzip|
+      gzip.write(MoonModel::DataSet::MAGIC)
+      gzip.write([encoded.bytesize].pack("L<"))
+      gzip.write(encoded)
+      gzip.write(elevations.pack("s<*"))
+      gzip.write(reflectance.pack("C*"))
+    end
+    path
+  end
+end
+
+class Minitest::Test
+  include TestData
+end