Self-Testing Procedures

Well almost. I use several methods but here’s my most common:

I want to write a small function to return me yesterday’s date as a formatted string. A useful function, because I’m often to tired to write the report at night time, so I write it the next day, but by then I want yesterday’s date on the report.

The function itself is straightforward enough:

Public Function strYesterDate() As String
strYesterDate = Format(Now() - 1, "YYYY/MM/DD")
End Function

Stop mumbling! The “Function strYesterDate() As String” part tells us that the procedure will return a string as the value of its name.

The body of the code reads “Format a date value as a YYYY/MM/DD format. What date value? Now (or today) less one, that is, yesterday.

I think it will work, but before I invest any time in manipulating the code or developing application code based on the new procedure, I draft a short test routine.

Mechanically I double-click on the procedure name to select it, Ctrl-C to copy the selected name to the clipboard, Ctrl-End to go past the end of the procedure, then I type "Sub TEST" and Ctrl-V to paste in the name of the procedure to be tested.

In this case (and most cases returning a string or numeric value) it will be enough for me to see the result in a pop-up box, so in the empty space provided for code I type “MsgBox” and a space and Ctrl-V to paste in the procedure name.

Not a lot of typing, really, is it?

Since the cursor is already in the code of my TEST macro, I tap the F5 function key to execute it and observe the formatted date in the pop-up box. Swell.

I don’t want to clutter up my user interface with a zillion TEST macros, so I comment out the TEST routine:

Public Function strYesterDate() As String
strYesterDate = Format(Now() - 1, "YYYY/MM/DD")
End Function
'Sub TESTstrYesterDate()
'    MsgBox strYesterDate
'End Sub

Then I drag it inside the procedure:

Public Function strYesterDate() As String
strYesterDate = Format(Now() - 1, "YYYY/MM/DD")
'Sub TESTstrYesterDate()
'    MsgBox strYesterDate
'End Sub
End Function

As an added advantage, the TEST code will travel wherever the procedure goes; if I make a change to the procedure, I can drag the TEST code out, de-comment it, and check that the procedure still behaves as it should after modifications.

Over the next few sessions we’re going to have you create a utility library, so that the excellent procedures you write will be available to you for ever, and will accelerate your development of applications.

Once you’ve grasped the idea behind a utility library, I’m going to offer you some free samples of useful code.

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