sinon stub as a module

Hi, I'm trying to do a test in a class written in ES6. The problem arises when I want to do a stub on a function of a module that I import.

the code I have is the following:

module.js

 function soapModule(){
      this.callSoap = (id) => {
         ....//some code
          return new Promise((resolve,reject) =>{
             return resolve("whatever");
          }
      }
 }

index.js (this is the index of the module)

 "use strict";

 var soapModule = require('./module/module');

 module.exports.soapModule = soapModule;

my-class.js

import {soapModule} from "soap-client"

export default class MyClass {

   constructor(){
     console.log("instance created");
   }

   myMethod(id){
     let sm = new soapModule();

     return sm.callSoap(id)
            .then(result => {
                console.log(result);
            }).catch(e => {
                console.log("Error :" + e);
            })
   }
}

test.js

import MyClass from "../src/my-class";
import {soapModule} from "soap-client";
import sinon from 'sinon';

describe("Test MyClass",()=>{

    let myclass;
    let soap;
    let stub;

    before(()=>{
        myclass = new MyClass();
        soap = new soapModule();
        stub = sinon.stub(soap,'callSoap');
    });

    it("test a", ()=>{
        let fakeout = {
            resp : "tada!"
        }
        stub.resolves(fakeout);
        myclass.myMethod(1);
    });
});

I think I'm not generating the stub well, since I can not get coverage of the code that is inside the .then