Cypress
Cypress is a free, open-source and locally installed, all-in-one testing framework and assertion library, which includes mocking and stubbing. Cypress gives the same power and control as well-established browser testing tools like Selenium, with a lower setup and operational overhead, and is worth considering as an alternative. While Cypress has many compelling features, it is worth being aware that currently only Firefox and Chrome-family browsers are supported, so it is not possible to perform a huge range of cross-browser testing.