Feature: Testing Global Errors in Karma

[ilyaigpetrov]

Setup

I need to test such function:

const testMe = () =>
  setTimeout(
    () => { throw new EvalError('foo'); },
    0,
);

Proposed Solution

it('throws error', (done) => {

  expect(testMe).to.eventually.throw.global(EvalError).then((thrown) => {

    expect(thrown.message).to.equal('foo');
    done();

  });

});

Current Solution

const catchGlobal = (errHandler) => {

  const originalOnError = window.onerror;
  window.onerror = () => {};
  window.addEventListener('error', (errEvent) => {

    window.onerror = originalOnError;
    setTimeout(() => errHandler(errEvent.error), 0);

  }, {
    capture: true,
    once: true,
  });

};

it('throws error', (done) => {

    catchGlobal((thrown) => {

      expect(thrown.message).to.be.equal('foo');
      done();

    });

});

Gory Details

1. In API of Chrome web-extensions you may pass callbacks.
2. If error is thrown in such callback, you can't catch it, except one case: error is thrown in setTimeout.
3. So you wrap all callbacks in setTimeout and set global error catchers. I wrote a few functions to automate this process, which I need to be tested.
4. For more details see: https://crbug.com/357568