The document discusses dealing with legacy code by implementing a "reversed tests pyramid" approach. It recommends starting with end-to-end tests to allow refactoring the codebase into a more testable structure before introducing unit and integration tests. While end-to-end tests are difficult to maintain, this process helps pay down technical debt over time by improving code quality and making the software easier to change. The key is to reverse the tests pyramid gradually through refactoring supported by tests at each level.

1. Reversed TTeessttss PPyyrraammiidd –– DDeeaalliinngg WWiitthh
LLeeggaaccyy CCooddee
Wiktor Żołnowski
@streser
http://www.agileszkolenia.pl
http://codesprinters.com
@pragmaticcoders
http://pragmaticcoders.com

2. Can you imagine perfect software?

4. Tests pyramid
End to End Tests
Functional/Integration Tests
Unit Tests

5. It would be perfect to work with perfect
software every day...

6. But!

7. Reality...

8. Is...

9. Different!

10. Legacy Code

11. How did we get to this point?

12. It's all because of the money...

13. Technical Debt

14. Sometimes Technical Debt could be
considered as something good...

15. Unfortunately temptation of easy
making money is huge...

16. People lives in illusion of continuous,
fast and low cost development...

17. Forgetting about the Quality...

18. Success in Software Development is something which is not
continuous...

19. Success is state that you can achieve but also lose very fast
if you can't respond to changes fast enough...

20. So, is it possible to deal with legacy code?

21. Reversed Tests Pyramid
End-to-End Tests
Functional/Integration Tests
Unit Tests

22. - What?!

23. You can't do unit testing when there are
no units in your software...

24. You can't do integration tests when
there is nothing to integrate...

25. You need to refactor your code so it
would be testable...

26. How to refactor without tests?!

27. Now refactor...
High level tests gives you courage to refactor your code...
●

28. But.. There are few reasons why you shouldn't
reverse tests pyramid
End-To-End tests are too long...

29. End-to-end tests are difficult to maintain...
If we need end-to-end tests we are probably doing something
wrong with our architecture...

30. So it's all about reversing back our
tests pyramid.

31. Step by step we are introducing new
architecture...

32. Remember that creating reversed tests
pyramid and reversing it back will take
some time...

33. But you need to do this if you want to
pay your technical debt back!

34. Few final thoughts...
Keep your technical debt as low as possible and try to
pay it back every time you can. For example use your
slack time for that!

35. Remember - WHY we are doing this?

36. “Leave the world better then you found it”

37. Beware of refactoring just for refactoring!
Few final thoughts...

38. Few final thoughts...
● Beware of refactoring just for refactoring!
● Resist temptation to re-write from scratch – history is against you,
such projects usually fail.
● Remember to always remove your (duplicated) tests!
● Software quality in many cases could be understood as ability to
introduce changes into software!
● Keep your technical debt as low as possible and try to pay it back
every time you can. For example use your slack time for that!
Resist temptation to re-write from scratch – history is
against you, such projects usually fail.

39. Few final thoughts...
● Beware of refactoring just for refactoring!
● Resist temptation to re-write from scratch – history is against you,
such projects usually fail.
● Remember to always remove your (duplicated) tests!
Remember to always remove your (duplicated) tests!
● Software quality in many cases could be understood as ability to
introduce changes into software!
● Keep your technical debt as low as possible and try to pay it back
every time you can. For example use your slack time for that!

40. False positive or false negative safety
net is even worst than lack of safety
net...

41. ● Software quality in many cases could be understood as
ability to introduce changes into software!

42. Wiktor Żołnowski
agileszkolenia.pl
Questions?
@streser
http://pragmaticcoders.com
http://codesprinters.com