how to test reduce function inside exports function Jest(react)

I have a reducer in react which I am testing I want to test the return value of a reduce inside the exports default function. And I'm not sure how to get access to the reduce inside that function.

MyReducer:

exports default function myReducer({
 people = [0,1,2];
 people.reduce(function(sum, peeps){
 return sum + peeps;
 }0);
 return "hey";
})

In jest test:

import myReducer from 'myReducer';
expectedPeeps = 3;
expect(Something needs to go here).toEqual(expectedPeeps);

I need to figure out how to get the return value of people.reduce. I can get "hey" by just invoking myReducer(). But how do I get the return value of people.reduce in my test! ?thanks in advance peeps.