What is Penelope doing at the end of book 20 in The Odyssey?

"This was her way of putting her husband to the test."

Penelope does not believe that it is really her husband who has returned. She thinks that a God or something else may be pretending to be Odysseus. Since he constructed the bed himself of course he would know that it was built into a tree truck and essentially cannot be moved. The test is her passively saying that the bed is going to be moved, if Odysseus would not have questioned the moving of the bed then it would of lead her to believe that it indeed was not Odyssues. The "test" was a way for her to find out if it was truly Odyssues.