Improve encoding test

test/engines/test_encoding.rb

@@ -1,13 +1,27 @@
-require 'minitest/autorun'
+require "minitest/autorun"
+
+# polyfill for Ruby 2.2 and down, used by minitest
+unless "".respond_to?(:match?)
+  String.instance_eval do
+    def match?(other)
+      (Regexp === other) ? other.match?(self) : (self == other)
+    end
+  end
+end
 
 class TestEncoding < Minitest::Test
-  def test_utf8
-    assert_equal("".encoding, Encoding::UTF_8)
+  def test_utf8_lang
+    assert_equal("en_US.UTF-8", ENV["LANG"])
+  end
+
+  def test_utf8_string
+    assert_equal(Encoding::UTF_8, "".encoding)
   end
 
   def test_read_utf8
-    contents = File.read('test/fixtures/encoding/utf-8.txt')
-    assert_equal(contents.encoding, Encoding::UTF_8)
-    assert_equal(contents, "\u2705\n")
+    contents = File.read("test/fixtures/encoding/utf-8.txt")
+
+    assert_equal(Encoding::UTF_8, contents.encoding)
+    assert_equal("\u2705\n", contents)
   end
 end