1. HOW TO TEST
UNTESTABLE CODE
Bruno BOUCARD @brunoboucard
#LearnToCraft

2. THE PROBLEM
NEED TO BE REFACTORED
NOT DESIGNED TO BE
TESTABLE

3. WHY?
NOT DESIGNED TO BE TESTABLE
Hardwired dependencies
 Database
 Network connection
 Third service
 Real time
 Random
 Singletons
 Statics

4. FACT - LEGACY CODE IS NOT DESIGNED TO BE TESTABLE

5. FACT - LEGACY CODE IS NOT DESIGNED TO BE TESTABLE

6. DON’T BE AFRAID BY A DAUNTING SITUATION
SO, HOW TO START?

7. DON’T BE AFRAID BY A DAUNTING SITUATION
SO, HOW TO START?
 Many classes
 Many lines of code
 Many warnings from Code Metrics
 Never built with testability in mind

8. CLEAN THE DECK
HOW TO START?

9. CLEAN THE DECK
HOW TO START?
Delete commented out and unused code
Makes the code easier to understand
You don’t want to write unnecessary tests
Tools like Resharper for .NET can help
The compiler is a reliable ally
Remember you have version control for
emergencies (hopefully)

10. DO NOT ATTEMPT A BIG BANG
HOW DO I KNOW THAT I‘M NOT BREAKING ANYTHING?

11. DO NOT ATTEMPT A BIG BANG
HOW DO I KNOW THAT I‘M NOT BREAKING ANYTHING?
Changing all the code to add unit tests
Will break everything!
Start small and work outwards
Velocity will be low initially
Should increase as test coverage increases
Use code coverage as a useful metric
But don’t be enslaved by it

12. HOW DO I KNOW THAT I‘M NOT BREAKING ANYTHING?
MOVE ON CAREFULLY

13. HOW DO I KNOW THAT I‘M NOT BREAKING ANYTHING?
MOVE ON CAREFULLY
Hyperaware Editing
Preserve Signatures
Single-Goal Editing
Lean on Compiler
Pair Programming

14. LIVE CODE
TRIPSERVICE
SHARED YOUR TRIP
AND HAVE FUN
Source : Sandro Mancuso
https://www.youtube.com/watch?v=_NnElPO5BU0

15. Bruno BOUCARD @brunoboucard #LearnToCraft
DON’T BE AFRAID BY A DAUNTING
SITUATION CLEAN THE DECK
DO NOT ATTEMPT A BIG BANG MOVE ON CAREFULLY
APPLY BREAKING
DEPENDENCIES TECHINQUES
HOWTOSTARTHOWTONOTBREAKANYTHING?
INSUMMARY