[gamegoblin]

I had written this comment[0] about our pattern here a few months ago and we decided to turn it into a full blog post.

It's crazy how many weird bugs you can detect with such a trivial method.

For applications like a spreadsheet that have a million overlapping features, it's impossible to manually write unit tests for every combination of features, so randomized tests do a lot of heavy lifting.

[0] https://news.ycombinator.com/item?id=40876726

[ForOldHack]

Unless your spread sheet can calculate unit tests, then it can combine tests in combinatorial fashion, and build Weinerstrauss test monsters. ( I am kidding on this last point, Spreadsheets will never operate in fractional dimensions. )

If, of course, you can calculate rule 110/124, then your spread sheet can be considered Turing complete.

"With LAMBDA, Excel has become Turing-complete. You can now, in principle, write any computation in the Excel formula language.Jan 25, 2021"."

The only caveat to Excel being Turing-complete is that it will never ever display the results properly.

[ForOldHack]

I tested Excel, and even early versions can calculate Rule 124. Now I have loaded it down with rotating a right triangle in 1/n radians. ( The right triangle has sides e+1/Pi and Pi+1/e. )...

Maybe your spreadsheet will do better?