From “City of Nets: A Portrait of Hollywood in the 1940s,” by Otto Friedrich. This is in a section on “Casablanca”: the making/marketing of:

There was such indecision about [which man Ilsa would choose] that the authorities finally decided to shoot both possibilities. “They were going to shoot two endings,” Miss Bergman said, “because they couldn't work out whether I should fly off by airplane with my husband or stay with Humphrey Bogart. So the first ending we shot was that I say good-bye to Humphrey Bogart and fly off with Paul Henreid. . . . And everybody said. ‘Hold it! That’s it! We don't have to shoot the other ending.' ” Even that ending, with Bogart and Rains walking off into the night, needed a closing line. One version was that Bogart would say, “Louis, I might have known you'd mix your patriotism with a little larceny.” Wallis claimed that he was the one who thought of something better: “Louis, I think this is the beginning of a beautiful friendship.” And even then, they didn't know what they had achieved.

At a sneak preview in Huntington Park, the audience seemed mildly pleased, but several viewers handed in cards that said the ending seemed unclear. Would Bogart and Rains be arrested? Wallis ordered a new closing scene written, in which Bogart and Rains escaped from Casablanca on a freighter. And somebody in the publicity department said a new title should be found, because Casablanca sounded like a brand of beer.

Can you imagine if they'd listened? Filmed more? Showed their flight out of Casablanca? But I assume most people in Hollywood know that if your test-screen audiences says they want more, then you‘ve got ’em.