In Book 18 of the Odyssey, what does Odysseus discover as he begins the testing of the women?
As he finds in many other instances, he learns that the maidservants have not necessarily been as loyal to him as he hoped. His long absence has basically left many of them to assume that he will never return and they begin to take advantage of the situation by flirting with the suitors and forgetting who they ought to be loyal to. Of course Odysseus reminds them of where their loyalty ought to lie when he scolds them fiercely and tells them to go join their mistress in her chambers rather than hanging out and partying it up with the suitors.
In Book 18 of the Odyssey, Odysseus finds out that some of the servant women have been loyal to him and some of them have them disloyal to him. Many of them are having sex with the suitors, which is a betrayal to Odysseus and his family. Some of them have been disloyal to Penelope by trying to find out her ploys and divulging information to the suitors.
Throughout the epic, Odysseus has been learning about loyalty. It is one of the major themes of the entire work. Many people in Ithaca are still loyal to him (including his swineherd Eumaios and his housekeeper Eurycleia), even after his twenty year absence. They are rewarded with his return. The disloyal people, like the servant girls who are sleeping with the enemy, are punished. In fact, Odysseus has twelve of the women, who are proven to be disloyal, put to death by hanging.