In this workshop we'll take a slice of a pretty standard PHP project and gradually work our way towards an application that has a better architecture. "Better" meaning that: It will be easy to find out what the uses cases of the application are ("screaming architecture") It will be easy to find a place for every piece of the application ("layers") It will be easy to find out how users and other systems can interact with it ("ports & adapters") It will be easy to provide tests and automated acceptance criteria for it ("the testing pyramid") I'm sure you would like your project to have these properties! I'll show you all the little steps that will help you transform your application to this new level.

1. ADVANCED
APPLICATION
ARCHITECTURE
I - Layers
Matthias Noback
@matthiasnoback

2. matthiasnoback/
layers-ports-and-adapters-
workshop
Clone from GitHub
docker-compose pull
bin/composer.sh install
docker-compose up -d

3. ARCHITECTURE
Decisions about coupling and cohesion

4. COUPLING
How are things linked to each other?

5. COHESION
Which things belong together?

6. LAYERED ARCHITECTURE
An answer to both questions

7. LAYERS
Help you protect what's in a deeper layer

8. LAYERS
Allow you to define dependency rules

9. LAYERS
Define the right place to put things

10. TRADITIONAL LAYERING
view
model
data

11. LAYERS
Horizontal division (as opposed to...)

12. USE CASES
Vertical division

13. LAYERS
Rendered as circles

14. CLEAN ARCHITECTURE
Or "union" architecture

15. COHESION
A basic set of layers
infrastructure
application
domain

16. COUPLING
The dependency rule
Layers should only depend on deeper layers

17. COUPLING
Dependency inversion principle
Classes should always depend on things that are more abstract

18. COUPLING
Dependency inversion principle
low-levelconcrete class specific
abstract interface generic high-level

19. COUPLING
Dependency inversion principle
use

20. COUPLING
Dependency inversion principle
use implement

21. COUPLING
Is about dependencies in code
Use Dependency Injection

22. LAYER CONVENTIONS
Domain layer
Domain model:
➤ Entities
➤ Value objects
➤ Domain services
➤ Factories
Business logic
Decisions
Data
State
Behavior

23. LAYER CONVENTIONS
Application layer
➤ Find an object
➤ Change something
➤ Notify something
➤ Get some information
Use cases
Orchestration

24. LAYER CONVENTIONS
Infrastructure layer
Communication with:
➤ HTTP client
➤ Database
➤ Filesystem
➤ Email server
➤ Message broker
Connecting the
application to
the world
outside

25. MATTHIASNOBACK/LAYERS-
PORTS-AND-ADAPTERS-
WORKSHOP
Assignments are on GitHub in assignments/

26. assignment/01.md
Layers

27. ADVANCED
APPLICATION
ARCHITECTURE
II - Ports & adapters

28. MESSAGING
... is the big idea

29. PORTS (COHESION)
Web, CLI, test client, messages, database queries
User interface
Persistence

30. PORTS... AND ADAPTERS
Translation
HTTP
SQL

31. HEXAGONAL ARCHITECTURE
Same thing!
User interface
Persistence

32. PORTS... AND ADAPTERS
(De)serialization, translation, structural validation
HTTP
SQL

33. assignment/02.md
Ports

34. PORT ADAPTERS
...in the Infrastructure layer

35. APPLICATION SERVICES
... in the Application layer

36. DOMAIN MODEL
in the Domain layer

37. APPLICATION SERVICES
Delivery-mechanism agnostic

38. assignment/03.md
Input adapters

39. VALIDATION
At different levels
Structural validation of messages
User-friendly input validation
Domain invariant protection

40. assignment/04.md
Input validation

41. APPLICATION SERVICES
Transactional consistency

42. assignment/05.md
Output adapter

43. assignment/06.md
A hidden dependency on the persistence mechanism

44. ADVANTAGES OF USING LAYERS,
PORTS & ADAPTERS
Offers insight into the application
Isolates the low-level details
Allows for alternative implementations
Helps with testing

45. ADVANCED
APPLICATION
ARCHITECTURE
III - Testing

46. UNIT TESTS
Testing your units of code
One class at a time
No IO
No setup required
Mocking only dependencies "you own"

47. INTEGRATION TESTS
Testing your adapters
Maybe multiple classes
Including IO
Some setup required
Mocking no dependencies

48. ACCEPTANCE TESTS
Testing your application services
Multiple classes
Use cases
Infrastructure stand-ins

49. SYSTEM TESTS
Testing your application end-to-end
The real deal

50. TESTING PYRAMID
Make it well-balanced
Unit
Integration
System
Acceptance

51. assignment/07.md
Different types of tests

52. ACCEPTANCE TESTS
Use infrastructure stand-ins
Acceptance test
test the
application
layer

53. Persistence
FileBased InMemory
Port
Adapters

54. MeetupRepository
FileBasedMeetupRepository InMemoryMeetupRepository
Domain
Infrastructure
implements implements

55. assignment/08.md
A test double for the Persistence port

56. assignment/09.md
An acceptance test for the application layer

57. A WELL-BALANCED TEST SUITE
Adapters can be easily replaced
Test suite is fast
Feedback is quick
Small amount of fragile tests
Enables continuous delivery

58. assignment/10.md
Notifications

59. https://training.matthiasnoback.nl/

60. https://joind.in/talk/b1763
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