Add test to prove threading works

spec/namae/threading_spec.rb

@@ -0,0 +1,25 @@
+module Namae
+  describe 'Parser using threads' do
+    let(:name_1_str) { "Foo Bar" }
+    let(:name_2_str) { "Baz" }
+    let(:name_1) { Namae.parse(name_1_str).first }
+    let(:name_2) { Namae.parse(name_2_str).first }
+
+    def compare(string, expectation)
+      name = Namae.parse(string).first
+      given_name_match = expectation.given == name.given
+      family_name_match = expectation.family == name.family
+      raise unless given_name_match && family_name_match
+    end
+
+    it 'has no conflicts' do
+      [[name_1_str, name_1], [name_2_str, name_2]].map do |string, expectation|
+        Thread.new do
+          1000.times do
+            compare(string, expectation)
+          end
+        end
+      end.each(&:join)
+    end
+  end
+end