Think about the personality of someone who is so dissatisfied with the lack of verbosity in his test suites, that he needs a side project of writing a book about unit testing. Of course they will advocate testing one assertion per function, and make up nonsense to justify their recommendation.

Secretly, they would have the reader write 32 functions to separately test every bit of a uint32 calculation, only refraining from that advice due to the nagging suspicion that it might be loudly ridiculed.