Jest: "Async callback was not invoked within timeout specified by Jasmine."

Hey there ! I'm trying to test Redux actions with Jest, using Promises.
My action function is the following :

export function exportCurrentConfig() {
    return function(dispatch, getState) {
        const result = postJSON( some_url_im_requesting, {})
            .then(data => {
                return (dispatch) => {
                    dispatch({
                        type: 'GET_EXPORT_ID',
                        payload: data
                    })
                }
            })
        return result
    }
}

This postJSON function is mocked :

// __mocks__/fetch.js
export function postJSON (url, data) {
    return new Promise((resolve, reject) => {
        process.nextTick(
            () => {}
        )
    })
}

and then, in my specs i'm trying to check the final result when all the promises are resolved :

// __tests__/components/exports-actions-test.js
jest.unmock('../')
jest.unmock('../actions')
jest.unmock('redux-mock-store')
jest.unmock('redux-thunk')

import * as actions from '../actions'
import configureMockStore from 'redux-mock-store'
import thunk from 'redux-thunk'

const middlewares = [thunk]
const mockStore = configureMockStore(middlewares)

describe('Dataset actions', () => {

it('exportCurrentConfig - default parameters', () => {
    const expectedActions = [{
        type: actions.GET_EXPORT_ID
    }]
    const store = mockStore({})
    return store
        .dispatch(actions.exportCurrentConfig({}))
        .then(() => {
                      expect(store.getActions()).toEqual(expectedActions)
            })
    })
})

The mock function is called and returning the promise, the action is returning something, but i'm getting this error on the specs :
Error: Timeout - Async callback was not invoked within timeout specified by jasmine.DEFAULT_TIMEOUT_INTERVAL. (using babel-jest 14.1.0 and jest-cli 12.0.2)

EDIT: Also tried to redefine the global definition of Promise, and it's also breaking the specs..

Thanks for your help !