Film: Scavenger Hunt (1979)

Mildred Carruthers (Cloris Leachman):"Why that worm. What's he trying to prove? Georgie and I are his legitimate heirs. Why should we have to play some dumb game just to get what's rightfully ours? I'm going to contest this will!"
Charles Bernstein (Robert Morley):"That's the point, Mrs. Carruthers. This will is a contest."
Scavenger Hunt

Scavenger Hunt is a 1979 comedy film starring, among others, Richard Benjamin, James Coco, Richard Mulligan, Ruth Gordon and Cloris Leachman. The plot centers around, well, Exactly What It Says on the Tin. Specifically, one arranged by the late game inventor Milton Parker (Vincent Price) for the $200 million in his will. There are five teams consisting of Mr. Parker's servants, his greedy widowed sister with her dumb son Georgie and their Amoral Attorney Sellsome, son-in-law Henry Motley (Tony Randall) and his four kids, nephews Kenny and Jeff Stevens, and cab driver Marvin Dummitz. (See below under No Celebrities Were Harmed.) Hilarity Ensues.

As usual, you can find the basics at The Other Wiki and at IMDB.

"This trope is a contest":