Jonathan's Pecha Kucha

1. Testable Code – Mind Shi2s

2. Testable Code – Mind Shi2s

3. Flaw: Constructor does Real Work

4. Flaw: Constructor does Real Work
• It violates the Single Responsibility Principle
• Tes7ng Directly is Difficult
• Subclassing and Overriding to Test is S7ll
Flawed
• It Forces Collaborators on You

5. Warning Signs

6. Warning Signs
• new keyword in a constructor or at field
declara<on
• Sta<c method calls in a constructor or at field
declara<on
• Anything more than field assignment in
constructors
• Adding or using an ini<aliza<on block

7. Warning Signs

8. Warning Signs
• Object not fully ini<alized a2er the constructor
finishes (watch out for ini<alize methods)
• Control flow (condi<onal or looping logic) in a
constructor
• CL does complex object graph construc<on
inside a constructor rather than using a factory
or builder

11. Solu<on
Do not create collaborators in your constructor,
but pass them in. (Don’t look for things! Ask
for things!)

12. Flaw: Digging into Collaborators
getUserManager().getUser(123).getProfile()
.isAdmin()
// this is egregiously bad (all you need to know if
the user is an admin)
context.getCommonDataStore().find(1234)
// this is bad

13. Warning Signs

14. Warning Signs
• Objects are passed in but never used directly
(only used to get access to other objects)
• Law of Demeter viola<on: method call chain
walks an object graph with more than one dot (.)
• Suspicious names: context, environment,
principal, container, or manager

17. Flaw: Bri9le Global State & Singletons

18. Flaw: Bri9le Global State & Singletons
• Spooky Ac<on at a Distance

19. Warning Signs

20. Warning Signs
• Adding or using singletons
• Adding or using sta<c fields or sta<c methods
• Adding or using sta<c ini<aliza<on blocks
• Adding or using registries
• Adding or using service locators

26. Flaw: Class Does Too Much

27. Flaw: Class Does Too Much
a.k.a. …
• Kitchen Sink
• Dumping Ground
• Class who’s Behavior has too many “AND’s”
• First thing’s KIll All The Managers (*See
Shakespeare)
• God Class
• “You can look at anything except for this one
class”

28. Warning Signs

29. Warning Signs
• Summing up what the class does includes the
word “and”
• Class would be challenging for new team
members to read and quickly “get it”
• Class has fields that are only used in some
methods
• Class has sta<c methods that only operate on
parameters

31. It
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