My bulletproofing of these tests was not yet sufficient. Although I have never had a failure in probably thousands of tests, one user submitted a PR which did fail testing NOW, fortunately not in a test that is required to pass. The problem is that it is not sufficient merely to set the cell value inside a do-while loop; it is necessary to calculate it in order to cache its result so that results based on that cell will be internally consistent.
No source code is changed for this PR, just some tests.
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