Continuity mistake: When the Boeing 747-200B initially taxis out from the gate, the flaps are set for take-off. After the stairs get hijacked, the remaining shots show the plane with the flaps retracted.
Continuity mistake: In the impound lot scene when Fletcher is talking with his ex-wife next to her jeep the driver side window starts to open. It's closed for most of her close up, then switches back to open when she is getting in the car. (00:37:10 - 00:37:57)
Character mistake: When Dana Appleton objects to Fletcher badgering Kenneth Falk, the judge overrules because Falk is Fletcher's witness. You still aren't allowed to badger your own witness in a trial, which the judge should certainly know.
Continuity mistake: At the end when Audrey is drinking booze during take off, Jerry says "I love you" to her. Her drink instantly empties itself despite being full in the previous shot.
Answer: As you said, he was testing to see if the wish was broken--by going up to an attractive woman and talking to her. While we don't hear what happens, he apparently said something a little too "forward" to her (probably more forward than he would have done otherwise, hence the "not as well as I had hoped"), and got slapped, so he knew that he was still under the wish's effects.
Chanteuse66
But I want to know what he said to the woman.
It's deliberately made unclear what he specifically said, because him getting slapped in the face is the gag that shows the audience that he's still under the spell. If we heard what he said, then we would know right away the new wish wouldn't have worked. It's ultimately up to the viewer's imagination to decide what he told the woman.
Phaneron ★