have rake test fail on trailing whitespace

Rakefile

@@ -86,6 +86,7 @@ task(:clean) { rm_rf 'dist' }
 desc "Run tests with PhantomJS"
 task :test do
   sh 'script/test'
+  Rake::Task[:check_whitespace].invoke
 end
 
 desc "Strip trailing whitespace and ensure each file ends with a newline"
@@ -96,6 +97,16 @@ task :whitespace do
   end
 end
 
+desc "Checks for trailing whitespace in source files and tests"
+task :check_whitespace do
+  flunked = false
+  flunk = lambda {|file, num| flunked = true; puts "#{file}:#{num}" }
+  Dir['{src,test,examples}/**/*.{js,html}'].each do |file|
+    File.open(file, 'r') {|f| f.each_with_index {|ln, num| flunk.call(file, num + 1) if ln.chomp =~ /\s+$/ } }
+  end
+  fail if flunked
+end
+
 desc "Generate docco documentation from source files"
 task :docco do
   verbose false do