I want to use column D as my automated testing column.  I want it to show Green if the test works and Red (with white ink) if it fails.  That way the spreadsheet should shout out at me if tests are failing.

• So I add another heading Pass/Fail and add the formula =IF(B2=C2,"pass","fail") into cell D2. 
• I quickly overtype cell C2 with “i” to check it works with a pass and it does.  Then I put in the word “blah” to check that the fail works and it does too.  I undo both of those and play around with Excel’s conditional formatting feature and make “true” show in Green background and “false” show in Red Background.

I now have a testing environment, of sorts, and a passing test.

That's right!  A passing test!  In green.  Just like traffic lights!  Yippee!

Let's add our second test.