apply  service to listBooks() - unit testing fail
apply  service to listBooks() - unit testing pass
apply  service to createBook() - unit testing fail
apply  service to createBook() - unit testing pass
apply  service to updateBook() - unit testing fail
apply  service to updateBook() - unit testing pass
apply  service to deleteBook() - unit testing fail
apply  service to deleteBook() - unit testing pass
cleaning source code