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Jeremy D. Miller -- The Shade Tree Developer

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Create new entry points to enable unit testing of Legacy code

If you've been reading the Shade Tree Developer this week you'll know that I'm fighting with a legacy component. I was trying to get a piece of code into NUnit to test my new functionality. A class in the stack works by giving it a key value to a record in the database. I tried for awhile to use an existing stored procedure to push in test data. Guess what I found? I had relational integrity issues with setting up the test data, but so what, that's just what a database is. I wasted a bit of time pushing past the referential integrity by getting the correct data and stumble right into security authorization being performed inside the f***ing stored procedure! It was about this time I remembered what I had been reading in the Feathers book on legacy code. Sometimes you have to change the code just to get it into the test harness. A quick "CTRL-ALT-M" action with ReSharper, and voila, an entry point into the business logic that bypasses the database and security checks. Add some ObjectMother magic to construct the fugly data structures, and I've got a working unit-ish test. Moral of the story? Don't be afraid to change the code first before writing a test (well, maybe afraid but not terrified). Remembering to backup and look for an easier way to write a test was probably a good idea too.

Published Jun 30 2005, 06:57 PM by Jeremy D. Miller

Filed under: Legacy Code

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Jeremy D. Miller -- The Shade Tree Developer said:

Tip #1 - Go get a copy of Michael Feather's "Working Effectively with Legacy Code" book.&nbsp; If you...

# May 4, 2006 11:16 AM

Jeremy D. Miller -- The Shade Tree Developer said:

In a conversation last week I was asked for my recommendations on how to retrofit automated testing and

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About Jeremy D. Miller

Jeremy began his IT career writing "Shadow IT" applications to automate his engineering documentation, then wandered into software development because it looked like more fun. Jeremy previously worked as a systems architect building mission critical supply chain software for a Fortune 100 company and learned agile development practices as a .Net consultant at ThoughtWorks, one of the pioneers of agile development. Jeremy is the author of the open source StructureMap (http://structuremap.sourceforge.net) tool for Dependency Injection with .Net and the forthcoming StoryTeller (http://storyteller.tigris.org) tool for supercharged FIT testing in .Net. Jeremy's thoughts on just about everything software related can be found on his weblog "The Shade Tree Developer" at http://codebetter.com/blogs/jeremy.miller, part of the popular CodeBetter site. Jeremy is a Microsoft MVP for C#.

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Jeremy D. Miller -- The Shade Tree Developer

Create new entry points to enable unit testing of Legacy code

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