Idioms of conclusion in English

a foregone conclusion

if you say that something is a foregone conclusion, you mean that it is a result that is certain to happen

The outcome of the vote is a foregone conclusion.

The result of the game was a foregone conclusion.

jump/leap to conclusions | jump/leap to the conclusion that…

to make a decision about somebody/something too quickly, before you know or have thought about all the facts

There I go again—jumping to conclusions.