foregone conclusion
A result that everyone expects to happen for sure.
A foregone conclusion is an outcome that seems so certain that it feels already decided before it even happens. When something is a foregone conclusion, people assume they know how it will turn out, even though technically it hasn't happened yet.
In a basketball game between a professional team and a group of third graders, the professionals' victory would be a foregone conclusion. Nobody needs to watch the game to know how it will end. When a student who has studied hard all year takes a simple quiz on material they've mastered, their success might feel like a foregone conclusion.
The phrase suggests that going through the actual process, whether it's a competition, vote, or test, seems almost pointless because everyone already knows what will happen. If your school holds an election and one candidate is so popular that everyone expects them to win easily, you might hear someone say, “It's a foregone conclusion,” before votes are even counted.
Sometimes people use this phrase too quickly, assuming an outcome is certain when it actually isn't. History is full of “foregone conclusions” that turned out differently than expected, reminding us that until something actually happens, there's always at least a small chance for surprise.