It’s a different platform yes – but this utility is used to do test driven development, and the concepts principles it applies may well be useful / transferable to Excel.

Ah yes – data sign, size, type and boundary cases for IFs and Lookups are classics.

For a simple build-a-wall calculation, I give 20 tests on pages 181-182 of my book.

Dick I think your approach makes sense. I tend to use a separate wb (rather than a text file) so I can read and write inputs/outputs easier, and check proportions are understandable. And the test runner is trivial – assign input values…calc all…assign outputs…repeat for x test cases.

The key factors are to get decent real world test cases, and to know what you are looking for. The classic is to forget to test negatives, in fact I’m going to have to go and check something I did the other day right now!

Oh, I just see DermotH has just mentioned them.

I created a couple of simple test routines that I always use:

Firstly, I run a routine that changes the cell background and pattern to one I would never use for every unlocked cell – I use this to verify that only the cells that are allowed input are unlocked.

Then, once this has been checked and agreed, I can run 1 of 2 other routines:

A. this just enters a 1 into every unlocked cell, which is used to test any sub-total and total functions; OR

B. in each worksheet data input into every unlocked cell starts at a selected number (default is 1), and is incremented by 1 for each subsequent unlocked cell within the worksheet. I use this to check where values are referenced in other cells in different worksheets, plus it is more useful to verify ratios and validations.

I specifically don’t state expected output values, as I want to be certain that I am getting the correct results. I know that I have to check the maths involved, but it is useful, as it stops you assuming that all is well if you get the number you want..

Low level, and very simple I know, but I find it extremely effective for what I do.

I generally setup several Data Tables and use the built in Data , Table command
The Table Command only allows 2 inputs and monitors a single output.

To get around this I wrote a 4D data table function which will take 8 inputs and monitor 4 outputs.
http://www.ianeva.info/Excel_Diversions/4D_Data_Table/4D_Data_Table.html

Always interested in any feedback

Back to Testing,
My other preference is to use graphical validation, wherein I will setup a chart and either adjust input variables or change using a slider the output variables.
This way several variables can be monitored, or comparison between variables ie No. Cars Produced, Total Cost of Production and Cost per Car.
The benefit of this is that hundreds of output variables can be scanned very quickly just by moving the slider up/down changing the key output variable.

Hui…