Jest: Cannot assign to read only property '...' of object '...'

Right now in the React repo this test…

fit('blah', () => {
  expect(document.createElement('div')).toBe(document.createElement('div'));
});

…fails with the following meaningless error message:

TypeError: Cannot assign to read only property ‘Symbol(impl)’ of object ‘[object DOMImplementation]’

Apparently @trueadm mentions that this broke sometime recently because of a change we made. (I don’t have details.) Its a pretty confusing behavior though.

[bvaughn]

To be clear, this issue is specifically about improving the error message 😄 because the current one is unhelpful and confusing.

[jcestibariz]

Same here, for me in:

expect(fn.mock.calls).toEqual([[element]]);

The assertion had failed because the expectation was incorrect. After the expectation was fixed the test passed.