Add test for detecting color proximity

github-linguist.gemspec

@@ -23,4 +23,5 @@ Gem::Specification.new do |s|
   s.add_development_dependency 'pry'
   s.add_development_dependency 'rake'
   s.add_development_dependency 'yajl-ruby'
+  s.add_development_dependency 'color-proximity'
 end

test/helper.rb

@@ -2,6 +2,7 @@ require "bundler/setup"
 require "minitest/autorun"
 require "mocha/setup"
 require "linguist"
+require 'color-proximity'
 
 def fixtures_path
   File.expand_path("../fixtures", __FILE__)

test/test_color_threshold.rb

@@ -0,0 +1,20 @@
+require_relative "./helper"
+
+class TestColorThreshold < Minitest::Test
+  include Linguist
+
+  def test_color_threshold
+    langs_with_colors = Language.all.reject { |language| language.color.nil? }
+    cp = ColorProximity.new(20, langs_with_colors.map(&:color))
+    failing_threshold = []
+    langs_with_colors.each do |lang|
+      state = cp.within_threshold?(lang.color[1..-1])
+      unless state.first
+        failing_threshold << [lang, state.last]
+      end
+    end
+    message = "The following languages have failing color thresholds. Please modify the hex color.\n#{failing_threshold}"
+
+    assert failing_threshold.empty?, message
+  end
+end