tc_helper.rb in axlsx-3.0.0.pre

- old
+ new

@@ -5,6 +5,8 @@
   add_filter "/vendor/"
 end
 
 require 'test/unit'
 require "timecop"
-require "axlsx.rb"
\ No newline at end of file
+require "axlsx.rb"
+# MIME detection for Microsoft Office 2007+ formats
+require 'mimemagic/overlay'