The first test screening of "Ghostbusters" (1984) was done only 3 weeks after the filming was completed. There were about 200 university students who were raucous. Reitman felt the screening without special effects would reveal if the story and the humour really worked. In the scene where Sigourney Weaver opens the refrigerator, it only displayed "Scene Missing" and had grease pencil marks all over it. The audience groaned during the scenes but they also had a good time. The movie had 90% audience approval even without the special effects.
("Ghostbusters: An Oral History", Jeff Labrecque, Entertainment Weekly, 2014 & "Ivan Reitman Recalls The Wild First Screening Of Ghostbusters And The One Character He Wasnโt Sure Would Work", Mike Reyes, Cinemablend, 2021)
P.S: On this day, 42 years ago, Ivan Reitman's "Ghostbusters" (1984) premiered in Westwood, California, USA.