where exactly have you seen excel forumalas to have tests? I have, in my early careers, gone knee deep into Excel macros and worked on c# automation that will

where exactly have you seen excel forumalas to have tests? I have, in my early careers, gone knee deep into Excel macros and worked on c# automation that will create excel sheet run excel macros on it and then save it without the macros. in the entire process, I saw dozens of date time mistakes in VBA code, but no tests that would catch them...