fails:Process.exec raises Errno::ENOENT for an empty string
fails:Process.exec raises Errno::ENOENT for a command which does not exist
fails:Process.exec raises an ArgumentError if the command includes a null byte
fails:Process.exec raises Errno::EACCES when the file does not have execute permissions
fails:Process.exec raises Errno::EACCES when passed a directory
fails:Process.exec with a single argument subjects the specified command to shell expansion
fails:Process.exec with a command array uses the first element as the command name and the second as the argv[0] value
fails:Process.exec with a command array coerces the argument using to_ary
fails:Process.exec with a command array raises Argument error if the Array does not have exactly two elements
