Legacy Coderetreat: Episode 1 – From Nothing to System Tests Codecast

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From Nothing to System Tests – Codecast

Blog post series

This blog post is part of a series about legacy coderetreat and legacy code techniques you can apply during your work. Please click to see more sessions about legacy code.


Before starting to change any legacy system you need to know you will not introduce any defects when changing the code. So one way would be to stay on the safe side and start writing some automated tests. These tests can be Golden Master type of tests, they can be Characterization Tests, or anything else that might give you this certainty of correct changes in a later stage.

This is a code cast in Java where I start covering with tests a simple code base. Please read the explanation of this technique in the Part 2 – From Nothing to System Tests blog post. Have fun!


This session has some prerequisites:

  • Good knowledge of unit testing and test doubles, especially mocks, stubs and fakes.
  • Very good knowledge of the programming language you use. You often need to use some hacks that will allow you not to change the existing code and be able to test it.
  • Open mind to new, sometimes mind-blowing, techniques and concepts.

Further it is very important to have good knowledge about software design, especially techniques of decoupling the existing code. It would be a good thing that any attendee would know about the SOLID Principles and have basic knowledge about Design Patterns.


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