index.js

const React = require('react');
const { expect } = require('chai');
const { shallow, configure } = require('enzyme');
const { createSandbox } = require('sinon');
require('react-dom'); // required by the enzyme adapter internally
const Adapter = require('enzyme-adapter-react-16');

configure({ adapter: new Adapter() });

var called = 0;

class Test extends React.Component {

  doSomething() {
    called++;
  }
  componentDidMount() {
    this.intervalId = setInterval(this.doSomething, 1000);
    console.log("Did Mount");
  }
  componentWillUnmount() {
    debugger;
    clearInterval(this.intervalId);
  }
  render() { 
    return React.createElement("div", null, null);
  }
}


describe('<Test/>', () => {
  const sandbox = createSandbox();
  const ss = {};

  before(() => {
      ss.clock = sandbox.useFakeTimers({
          loopLimit: 50,
      });
  });

  afterEach(() => {
      sandbox.resetHistory();
  });

  after(() => {
      sandbox.restore();
  });

  it('should stop after unmount', () => {
      shallow(React.createElement(Test, null, null))
          .unmount();

      console.log(ss.clock.timers);
      debugger;
      ss.clock.tick(10000);
      console.log(ss.clock.timers);
      expect(called).to.equal(1);
  });
});