//app.test.js
import * as app from './app';


describe('spy example', () => {

    it('spy example', () => {

        const spy = jest.spyOn(app, 'func1');
        app.func2();
        expect(spy).toHaveBeenCalledTimes(1);
    });

});
//app.js
export const func1 = () => {

}

export const func2 = () => {
    func1();
}