The document discusses controversial software development ideas proposed by Lior Bar-On. It argues that inheritance violates object-oriented principles like encapsulation and polymorphism. It promotes composition over inheritance, claiming objects should use other objects rather than inheriting from them. The document also advocates reducing unit testing in favor of more integrated tests or production monitoring, arguing unit tests are expensive and other techniques can achieve high quality more cost-effectively. In general, it promotes questioning common practices and considering alternatives.

1. Software
Punk
Lior Bar-On, 2016
Controversial ideas in
Software Development
That just might work.
Source: songpop.wikia.com

2. Who is this Guy? (Lior Bar-On)
‫תוכנה‬ ‫ארכיטקטורת‬ ‫בלוג‬
Developer
Architect
Chief Architect
Blogger

3. Inheritance & OO
Source: schedule.sxsw.com

4. Inheritance is a bold violation of OO Principles!
1. Encapsulation (“‫)”הכמסה‬
2. PolyMorphism (“‫)”ריבוי-צורות‬
3. Inheritance (“‫)”הורשה‬
Violation

5. Flawed Inheritance Code Example

6. Composition > Inheritance
“... our second principle of object-oriented design:
Favor object composition over class inheritance.
”
Source: http://slidedeck.io/parnurzeal/why-opensource-slides Source: Addison wesley

7. A moment of Skepticism...
while (condition_always_true) {
// do something
...
}

8. Inheritance as tool for (poor?) abstractions

9. Inheritance as tool for (poor?) abstractions

10. Inheritance as tool for (poor?) abstractions
?

11. Inheritance as tool for (poor?) abstractions

12. Inheritance as tool for (poor?) abstractions
?

13. Inheritance as tool for (poor?) abstractions
?

14. Inheritance as tool for (poor?) abstractions
?

15. Inheritance as tool for (poor?) abstractions
Black Cab → A, B, C, D
Yellow Cab → A, E, F
Green Cab → A, B, D, E
Scooter → C, E, G
PHV → B, C, F

16. Inheritance breaking our reading flow
?
?

17. Recap
Inheritance can cause “unexpected behavior” -
but it is rare.
Inheritance (“is-a” delegation) is too limited to
expressed real world domain objects.
Use Inheritance only with dead-simple cases.
1
2
In some programming languages, Inheritance
makes the code less expressive.3

18. Bad, bad Abstractions

19. D.R.Y Happiness!
DRY = Don’t Repeat Yourself Source: dreamstime

20. D.R.Y Happiness @Gett-API

21. HTTP Retry: The POST case
...
IDEMPOTENT_METHODS = [“GET”, “PUT”]
if method in IDEMPOTENT_METHODS {
// http request retry
}
...

22. HTTP Retry: The POST case #2
...
if can_retry {
if _err == CONNECTION_ERROR {
// http request retry
}
} ...

23. The Safe Methods case
...
if method == “GET” {
// use cache
}
...

24. The Safe Methods Case #2 - POST (reading)
...
if is_cacheable {
// use cache
}
...

25. Cache TTL settings
...
// some logic with cache times...
...

26. The Fallback cache Case
...
if _err == CONNECTION_ERROR {
// try to load response from fallback cache
}
...

27. Not very DRY, but simpler!

28. Code Duplication is mushrooming

29. The non-visible dependencies of that system...

30. Recap
Not only code Rots. Abstractions Rot too.
It’s okay to occasionally favor Code Duplications
and avoid non-meaningful abstraction.
When an Abstraction rots: Stop. do a reverse,
and return the code duplication.
1
2

31. You Spend too much
on Unit Tests

32. Automation “should” improve things...
Source: Lucidcharts

33. There are several ways to achieve
high quality....
Source: profiles.com.sg

34. Type A: Codename “Lisa” (a Unit Test)
Source: a presentation by Lior Bar-On

35. Type A: Codename “Lisa” (a Unit Test)
Source: a presentation by Lior Bar-On
Isolated unit test

36. Type B Codename “Bart”
Source: a presentation by Lior Bar-On

37. Type B Codename “Bart”
Source: a presentation by Lior Bar-On
Unit-Integration Test
Integration Test

38. Type B Codename “Bart”
Source: a presentation by Lior Bar-On
Example: Aggregating 11 model
methods into a single test

39. Type C - Codename “Cat In The Hat”
Source: marocdeserttours.wordpress.com

40. Type C - Codename “Cat In The Hat”
Great Production Monitoring
/w Continuous Deployment

41. Type C - Codename “Cat In The Hat”
Source: marocdeserttours.wordpress.com
Ideal Target: when covering 90%+
of the cases is not possible
- or just too expensive

42. Recap
Unit Tests is great - but it has its costs.
It fit perfectly for logical code units (if / for)
Integration / Unit-Integration tests are more
broad - but more cost efficient.
1
2
Sometimes, it worth monitoring things only on
production.
When done well - it can be cheap, otherwise -
very expensive.
3

43. Don’t take things for
granted