I also wanted to test if `innerText` is used if `textContent` is not present. But now that I think about it... maybe this is not needed since if that wasn't done IE8 would not pass other unit tests, right?

Anyway, what I wanted to test as well is if `innerText` is not checked at all. I should add a test for that (I forgot after all, haha) but my rationale was that if I just changed the code to:
```js
return hiddenPre.textContent || hiddenPre.innerText || '';
```
i.e. just swapped the order of checked properties then the test for `"MOCK_TEXTCONTENT"` would pass; even if I set `textContent` to an empty string it would pass but `innerText` would be accessed anyway, causing unnecessary reflow. So I need to be able to provide different `textContent` for different tests anyway. And if both `textContent` and `innerText` were empty strings, the only way to check if the latter was accessed is through getters.

Am I over-engineering here? :)