Mockist vs. Classicists TDD

Mockist vs. Classicist TDD
Softwerkskammer Regionalgruppentreffen München
30.10.2014
David Völkel

Agenda
●Theory
●Pizza
●Kata

Classicists vs. Mockists
●Who knows?

Classicists vs. Mockists
●Who knows?
●Who leverages what?

How i stumbled upon…
●#GOOS
●#IsTDDDead
●Outside-In 
●Mocking 
●=> How work Classicist?

Classicists
●„old school“: Kent Beck, Uncle Bob, …
●state verification
●bottom-up/inside-out
●Avoid mocks when possible

Mockists
●„London School“: Steve Freeman, Nat Pryce
●XP 2000 „Endo-Testing: Unit Testing with Mock Objects “
●OOPSLA 2004 „Mock Roles, not Objects“
●Book „Growing Object Oriented Software“ #GOOS 2009

Mockists
●ATDD
●Outside-In Design
●Hexagonal / Ports&Adapters Architecture
●also for classicists
●Mocking to isolate layers
●Interaction based testing
●„Back-door“

Architecture
●Mockist OO-style
●Message Passing/Event-Architecture
●Topology / Message flow
●„Tell don‘t ask“
●Classicist FP-style
●mutable objects encapsulating state
●pure functions & immutable value objects
●details: algorithms, logic, conditionals

Layer
UI
Domain
Data Access
DB

Domain
Hexagonal / Ports & Adapters
UI
Domain Service
Repository DB Adapter
DB
Repository Interface

Hexagonal / Ports & Adapters
Domain Service
Repository DB Mock
DB
Unit Test

ATDD
From Growing Object-Oriented Software by Nat Pryce and Steve Freeman

Outside-In Design
UI
Domain Service
DB
End2End Test

Outside-In Design
UI
Domain Service
DB
Domain Service Interface
Unit Test
End2End Test

Outside-In Design
UI
Domain Service
DB
Unit Test
Unit Test
End2End Test

Outside-In Design
UI
Domain Service
DB
Unit Test
Unit Test
Integration
Test
End2End Test

Classicists Design
●Bottom-up
●emergent
●„TDD as if you meant it“ (YAGNI?)
●Middle ground?
●Acceptance tests => Domain

Classicist IO
out = pureFunction(in);
object.changeStateBasedOn(in);
out = object.getState();
●Functional
●State-based

Mockist IO: CQS
public Object myQuery() {
return neighbour.query();
}
when(neighbour.query()).thenReturn(in);
●Queries: Stubbing indirect input

Mockist IO: CQS
public Object myQuery() {
return neighbour.query();
}
when(neighbour.query()).thenReturn(in);
private void myCommand() {
neighbour.command(out);
}
verify(neighbour).command(out);
●Queries: Stubbing indirect input
●Commands: Spies check indirect output

Let‘s code!
●Content: Kata „Game of Life“
●Phase 1: Outside-In Mockist style
●Mockless Classicist design
●Phase 2: refactor to mockless Classicist design
●Mode: Mob Programming
●1 Driver
●N Navigators
●Variant: David = PO & facilitator

Classicist Isolation
●No isolation = „front door“
●Leaf
●Integrated test
●By design
●Context independence: parameterize methods/constructors, values/value objects, intermediary results
●„Functional Core, Imperative Shell“

String renderMail(String mail) {
String name = userRepo.nameFor(mail);
return renderMailAndName(mail, name);
}
@Test public void renderMail() {
when(userRepo.nameFor("customer@gmail.com"))
.thenReturn("Joe Customer");
assertEquals("customer@gmail.com <Joe Customer>",
mailService.renderMail("customer@gmail.com"));
}
Isolation via mocks

String renderMail(String mail) {
String name = userRepo.nameFor(mail);
return renderMailAndName(mail, name);
}
when(userRepo.nameFor("customer@gmail.com"))
.thenReturn("Joe Customer");
mailService.renderMail("customer@gmail.com"));
}
mailService.renderMailAndName("customer@gmail.com", "Joe Customer"));
}
Mockless isolation

Bilder
von RaminusFalcon
http://commons.wikimedia.org/wiki/File:Split- scissors.svg?uselang=de

Lizenz
Creative Commons Attribution-ShareAlike 3.0
https://creativecommons.org/licenses/by-sa/3.0/de/

TDD as if you meant it
1.Write exactly one failing test
2.Make the test pass by writing implementation code in the test method
3.When duplication is spotted extract the implementation from tests to:
1. a new method in the test class
2.an existing method in the test class
4.When more methods belong together extract them into a new class
5.Refactor as required
by Adi Bolboaca

Mockist vs. Classicists TDD

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