Autotest.add_hook :initialize do |at|
  at.clear_mappings
 
  at.add_mapping %r%/^lib/(.*)\.rb$% do |_, m|
    possible = File.basename(m[1])
    files_matching %r%^test/.*(#{possible}_test|test_#{possible})\.rb$%
  end
 
  at.add_mapping(%r%^test/.*\.rb$%) {|filename, _| filename }
end