mabeyj/qunit — comment on commit ee156923cdb01820e35e6bb579d5cf6bf55736d4
File: qunit/qunit.js line 1005
By mabeyj:

If it was that, then it wouldn't extend the `window` object at all (line 513). In that case, you wouldn't be able to call, for example, `test()` instead of `QUnit.test()`.

I figured it was safest to exclude `window.constructor` specifically, since the original code would override all constructors.