Best way to update an old VB6 app

Question

A small ma and pa shop came to me recently with a request to update a vb6 program one of their former part time employees made for them while home from college. On the cd the student provided is both the source code and a installer for the program, which extremely helps. I would like to just give them a new cd with a new installer and the updated source code. My question is, how do I go about creating or if easier updating a installer for a language that entered "Non Supported Stage" back in 2008?

Update: Just to answer some of the questions, the updates they are asking for are just changing the wording of some labels and changing one control from a textbox to a combobox. They are a ma and pa shop and don't want to pay the cost to have the app re-written to a newer language, even though it has been recommended.

Answer 1

You're going to need a copy of Visual Basic 6 (or Visual Studio 6) which is difficult. If you have an MSDN subscription, I'm quite sure you can download it from their archive, but if not, you might need to buy a copy. Check EBay. Have the ma and pa shop purchase it at their own expense, and they should own it in case they want to make future changes. You can use it on their behalf to do work for them, if you're the only one using it, and just uninstall it when you're done.

Also, if you have a copy of Visual Studio 2005, technically you can "downgrade" to VS6 but you have to call Microsoft and have them send you the install program, and you're not allowed to use VS2005 concurrently with VS6. Yeah, I know...

Ok, so if you've got that far, get the source on your computer and get it under source control. I suggest Mercurial (specifically the TortoiseHg client). I've had lots of luck with it on a VB6 project, and it's free. (Don't use SourceSafe, even if it comes free with VS6!) The distributed nature of the Mercurial repository means you can hand them back a CD with the entire repository on it, and the next poor sap who has to make changes will at least be able to do a diff and know what you did.

As someone else here said, VB6 has a built-in utility for making install programs, but I think you had to have the Enterprise version for that. It's worth finding that out before you get a copy.

Now go ahead and make changes, but be very careful. Remember that you probably don't have any unit tests, so you're likely to break stuff. If you want to be professional about it, there are unit testing frameworks out there for VB6. For instance, vbUnit. Again, I suggest having the customer buy a copy (about $99 for a single developer seat, I think). If the change was anything more than changing the company logo on the splash screen, then this is something I'd invest in. Write tests that cover every module or feature you're going to change. If all the logic is in event handlers in the form itself, carefully remove the code you need to change out into modules that you can write unit tests for. Write the tests to verify the current functionality first.

Then go ahead and make your changes. If you've gone to the trouble of setting up a testing framework, then you might as well use some TDD and write your tests first. Write a test, make sure it fails, write enough code to make it pass, and repeat.

All of this still requires you to have a solid manual test plan to check the functionality at the end. That means you need a solid grasp of what it does. You can pretty much assume that no matter how careful you are, you'll break something you didn't understand. Make sure to give yourself enough time to fix other problems that pop up after you deliver it.

I recommend against re-writing it in .NET unless it's a really simple program with only one form. The effort likely isn't worth it.

Caveat: beware of 3rd party components the original programmer might have used, but not included on the CD. If they used some ActiveX or COM stuff that they purchased from a 3rd party, but they didn't license it to your customer, you might have to end up purchasing it again just to get it to compile.

EDIT:

Based on your extra information, if you're really just changing a couple of controls and wording, then I think you can get away without a unit testing framework. I would definitely use some source control though.

I do remember using the Package and Deployment Wizard, and I agree it sucked. I actually used a 3rd party installer, now that I think about it. However, if the changes are small and the original application used the PDW, I'd probably stick with that.