in jest
(idiomatic) As a joke.
He only tried to mimic the other's movements in jest.
Chekhov’s gun is there on every page: words spoken carelessly or in jest are later repeated in a court of law, their meaning twisted; gifts given in innocence are produced with new motives ascribed. Source: Internet
Bester says that he replied (in jest), "You sonofabitch. Source: Internet
Hertel went on to speak of their conversations, which ranged from input from Hayden, arguments held in jest, and her disappointment at not seeing her students. Source: Internet
Before adding in jest: "And my husband is still alive." Source: Internet
If a fly can fly, we used to ask in jest all those centuries ago, why can’t a mosquito mosquito? Source: Internet
Miranda Hart, who recalls a visit to hospital for an enema, comes a close second as she wonders, perhaps in jest, whether she would get “preferential treatment because of the whole fame thing”. Source: Internet