addMarker work fine, but mocha see it as undefined while test

[moonbrv]

Hello, i write small piece of code, as in tutorial:

const map = new GMaps({
  el: '#map',
  lat: this.props.lat,
  lng: this.props.lng,
});

map.addMarker({
  lat: this.props.lat,
  lng: this.props.lng,
});

my App works fine, but when i decide to add some Mocha's tests to my components i saw message:

TypeError: map.addMarker is not a function

I'm not understand how it could be.
I write some test:

console.log(typeof GMaps); // function
console.log(typeof GMaps()); // function
console.log(GMaps().toString()); // function () {}

May be it is because i'm in node env. But how can I fix that situation? How to make tests?