Some XPath Tests for the plist

• There is a CFBundleExecutable:
  boolean(//key[. = 'CFBundleExecutable'])

• There is exactly one CFBundleIconFile:
  count(//key[. = 'CFBundleIconFile']) = 1

• The software is copyrighted by Mozilla:
  contains(//key[. = 'CFBundleGetInfoString']/following-sibling::string, '© 2005 The Mozilla Organization')

• The CFBundleSignature is four letters:
  string-length(//key[. = 'CFBundleSignature']/following-sibling::string) = 4

• No two key elements are adjacent:
  count(//key/following-sibling::*[1]/self::key) = 0