fails:File.unlink returns 0 when called without arguments
fails:File.unlink deletes a single file
fails:File.unlink deletes multiple files
fails:File.unlink deletes read-only files
fails:File.unlink raises an TypeError if not passed a String type
fails:File.unlink raises an Errno::ENOENT when the given file doesn't exist
fails:File.unlink raises Errno::ENOENT if filename is empty
fails:File.unlink coerces a given parameter into a string if possible
