Screencast: Testing and Refactoring Legacy Code
In this screencast I take a small piece of legacy Java code that contains the most common problems found in much larger legacy code bases. The objective is to first write tests to understand what the code does and then refactor it to make it better. The code contains Singletons, static calls and behaviour that does not belong there. It also has some design issues.
As an advice, I always recommend that we should never "touch" the production code as we retrofit tests, that means, we should not change it typing into the production file. However, as normally legacy code is not written with testing in mind, sometimes we need to change the production code in order to write tests for it. I address this scenario explaining how we can do that in a very safe way.
A common question when developers want to make legacy code better is "Where do we start?" I also address that explaining the how the approaches for testing and refactoring legacy code are the opposite from each other.
Besides a few other things, I also cover the use of code coverage tools to help us testing the code, how often we should be committing, how to fix a possible problem with the design in very small steps and how to stay in the green while refactoring our code.
Last but not least, I show how our tests and production code be easily written in a way that it captures the business requirements.
Although it is a bit long, I hope you all enjoy it.
There are two minor things I forgot to do while doing this exercise. Let me know if you spot it. :)
Published at DZone with permission of Sandro Mancuso, author and DZone MVB. (source)As an advice, I always recommend that we should never "touch" the production code as we retrofit tests, that means, we should not change it typing into the production file. However, as normally legacy code is not written with testing in mind, sometimes we need to change the production code in order to write tests for it. I address this scenario explaining how we can do that in a very safe way.
A common question when developers want to make legacy code better is "Where do we start?" I also address that explaining the how the approaches for testing and refactoring legacy code are the opposite from each other.
Besides a few other things, I also cover the use of code coverage tools to help us testing the code, how often we should be committing, how to fix a possible problem with the design in very small steps and how to stay in the green while refactoring our code.
Last but not least, I show how our tests and production code be easily written in a way that it captures the business requirements.
Although it is a bit long, I hope you all enjoy it.
There are two minor things I forgot to do while doing this exercise. Let me know if you spot it. :)
(Note: Opinions expressed in this article and its replies are the opinions of their respective authors and not those of DZone, Inc.)
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Myeongseok Baek replied on Fri, 2012/12/28 - 12:17am
Excellent screencast !!
You can use moreUnit(http://moreunit.sourceforge.net/) in order to switch between production and test code.
IMHO, you can use more IDE's automation features when you find feature envy(isFriendsWith method).
- extract method first
- move method to User class
What do you think about my opinion ?
Thanks