Depuis des années, j'ai constaté que je n'écris plus de classes abstraites dans mon code et je me suis donc posé la question "Pourquoi je n'ai plus de classes abstraites dans mon code ?". En creusant la question, je me rends compte que c'est depuis que j'ai commencé à appliquer le TDD ("Test-Driven Development" ou développement dirigé par les tests). Mais quel est le rapport entre les deux ? C'est ce que je vais tenter d'expliquer via ce talk.

1. Les classes abstraites,
c’est fini !
(et c’est la faute à TDD)
@DorraBartaguiz

2. http://www.nickelodeonjunior.fr/dora-l-exploratrice/
Dora l’exploratrice
@DorraBartaguiz

3. Dorra Bartaguiz
Dev / Craft coach
Co-auteure & illustratrice
@DorraBartaguiz
iAmDorra
@DorraBartaguiz

4. Dorra Bartaguiz
Rédactrice en chef du numéro 250
100 % féminin
Janvier 2022
@DorraBartaguiz
iAmDorra
@DorraBartaguiz

5. Discussion
Livre « Software Craft » - Edition Dunod
@DorraBartaguiz

6. Besoin métier
@DorraBartaguiz

7. Contexte
• Chaine de garagistes (France & Luxembourg)
• Calcul total d’une prestation à partir d’un montant hors taxe
• Calcul de la taxe en fonction du pays
• France 19.6%
• Luxembourg 15% sur le matériel & 12% sur le service
@DorraBartaguiz

8. Exemple
• En France
• 150€ HT & 19.6% taxe
• Total : 179,4€ TTC
• Au Luxembourg
• 100€ HT de matériel & 15% taxe de matériel => total matériel : 115€
• 50€ HT de service & 12% taxe de service => total service : 56€
• Total : 171€
@DorraBartaguiz

9. TDD
Test Driven Development
@DorraBartaguiz

10. TDD
• Kent Beck – 1990
• Ecrire le code de test avant le code de production
• Fixer l’objectif du besoin
• Définir à l’avance le comportement attendu
@DorraBartaguiz

11. TDD
@DorraBartaguiz

12. Besoin du garagiste
• En France
• 150€ HT & 19.6% taxe
• Total : 179,4€ TTC
• Au Luxembourg
• 100€ HT de matériel & 15% taxe de matériel => total matériel : 115€
• 50€ HT de service & 12% taxe de service => total service : 56€
• Total : 171€
@DorraBartaguiz

13. Disclaimer
@DorraBartaguiz

14. Garagiste en France
• 150€ HT & 19.6% taxe
• Total : 179,4€ TTC
Calculate_total_price_including_tax_for_french_mechanic()
{
var frenchTax = 0.196;
var preTaxPrice = 150;
var frenchPrice = new FrenchPrice(frenchTax, preTaxPrice);
var total = frenchPrice.CalculateTotal();
Check.That(total).IsEqualTo(179.4);
}
@DorraBartaguiz

15. Garagiste en France
• 150€ HT & 19.6% taxe
=> Total : 179,4€ TTC FrenchPrice
-preTaxPrice
-tax
+CalculateTotal()
public double CalculateTotal()
{
return preTaxPrice + preTaxPrice * tax;
}
@DorraBartaguiz

16. Garagiste au Luxembourg
• 100€ HT de matériel & 15% taxe de matériel => total matériel : 115€
• 50€ HT de service & 12% taxe de service => total service : 56€
• Total : 171€
Calculate_total_price_including_tax_for_luxembourgish_mechanic()
{
var preTaxServiceAmount = 50;
var serviceTax = 0.12;
var preTaxMaterialAmount = 100;
var materialTax = 0.15;
var luxembourgishPrice = new LuxembourgishPrice(preTaxServiceAmount, serviceTax,
preTaxMaterialAmount, materialTax);
var total = luxembourgishPrice.CalculateTotal();
Check.That(total).IsEqualTo(171);
}
@DorraBartaguiz

17. Garagiste au Luxembourg
• 100€ HT de matériel
• 15% taxe de matériel
=> total matériel : 115€
• 50€ HT de service
• 12% taxe de service
=> total service : 56€
=> Total : 171€
LuxembourgishPrice
-preTaxServiceAmount
-serviceTax
-preTaxMaterialAmount
-materialTax
+CalculateTotal()
public double CalculateTotal()
{
return CalculateVat() +
CalculatePreTaxAmount();
}
private double CalculateVat()
{
return preTaxServiceAmount * serviceTax +
preTaxMaterialAmount * materialTax;
}
private double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
@DorraBartaguiz

18. <<Interface>>
Price
+CalculateTotal()
FrenchPrice
-preTaxPrice
-tax
+CalculateTotal()
LuxembourgishPrice
-preTaxServiceAmount
-serviceTax
-preTaxMaterialAmount
-materialTax
+CalculateTotal()
public double CalculateTotal()
{
return preTaxPrice + preTaxPrice * tax;
}
public double CalculateTotal()
{
return CalculateVat() +
CalculatePreTaxAmount();
}
private double CalculateVat()
{
return preTaxServiceAmount * serviceTax +
preTaxMaterialAmount * materialTax;
}
private double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
@DorraBartaguiz

19. <<Interface>>
Price
+CalculateAmount()
FrenchPrice
-preTaxAmount
-tax
#CalculateVat()
#CalculatePreTaxAmount()
<<Abstract>>
BasePrice
+CalculateTotal()
#CalculateVat()
#CalculatePreTaxAmount()
LuxembourgishPrice
-preTaxServiceAmount
-serviceTax
-preTaxMaterialAmount
-materialTax
#CalculateVat()
#CalculatePreTaxAmount()
protected override double CalculateVat()
{
return preTaxAmount * tax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxAmount;
}
public double CalculateTotal()
{
return CalculateVat() + CalculatePreTaxAmount();
}
protected abstract double CalculateVat();
protected abstract double CalculatePreTaxAmount();
protected override double CalculateVat()
{
return preTaxServiceAmount * serviceTax +
preTaxMaterialAmount * materialTax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
https://fr.wikipedia.org/wiki/Classe_abstraite
@DorraBartaguiz

20. <<Interface>>
Price
+CalculateAmount()
FrenchPrice
-preTaxAmount
-tax
#CalculateVat()
#CalculatePreTaxAmount()
<<Abstract>>
BasePrice
+CalculateTotal()
#CalculateVat()
#CalculatePreTaxAmount()
LuxembourgishPrice
-preTaxServiceAmount
-serviceTax
-preTaxMaterialAmount
-materialTax
#CalculateVat()
#CalculatePreTaxAmount()
protected override double CalculateVat()
{
return preTaxAmount * tax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxAmount;
}
public double CalculateTotal()
{
return CalculateVat() + CalculatePreTaxAmount();
}
protected abstract double CalculateVat();
protected abstract double CalculatePreTaxAmount();
protected override double CalculateVat()
{
return preTaxServiceAmount * serviceTax +
preTaxMaterialAmount * materialTax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
« Design Patterns: Elements of Reusable Object-Oriented Software » écrit par Erich Gamma, Richard Helm, Ralph Johnson, et John Vlissides, avec une préface de Grady Booch
@DorraBartaguiz

21. <<Interface>>
Price
+CalculateAmount()
FrenchPrice
-preTaxAmount
-tax
#CalculateVat()
#CalculatePreTaxAmount()
<<Abstract>>
BasePrice
+CalculateTotal()
#CalculateVat()
#CalculatePreTaxAmount()
LuxembourgishPrice
-preTaxServiceAmount
-serviceTax
-preTaxMaterialAmount
-materialTax
#CalculateVat()
#CalculatePreTaxAmount()
protected override double CalculateVat()
{
return preTaxAmount * tax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxAmount;
}
public double CalculateTotal()
{
return CalculateVat() + CalculatePreTaxAmount();
}
protected abstract double CalculateVat();
protected abstract double CalculatePreTaxAmount();
protected override double CalculateVat()
{
return preTaxServiceAmount * serviceTax +
preTaxMaterialAmount * materialTax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
@DorraBartaguiz

22. <<Interface>>
Price
+CalculateAmount()
FrenchPrice
-preTaxAmount
-tax
#CalculateVat()
#CalculatePreTaxAmount()
<<Abstract>>
BasePrice
+CalculateTotal()
#CalculateVat()
#CalculatePreTaxAmount()
LuxembourgishPrice
-preTaxServiceAmount
-serviceTax
-preTaxMaterialAmount
-materialTax
#CalculateVat()
#CalculatePreTaxAmount()
protected override double CalculateVat()
{
return preTaxAmount * tax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxAmount;
}
public double CalculateTotal()
{
return CalculateVat() + CalculatePreTaxAmount();
}
protected abstract double CalculateVat();
protected abstract double CalculatePreTaxAmount();
protected override double CalculateVat()
{
return preTaxServiceAmount * serviceTax +
preTaxMaterialAmount * materialTax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
Non
instanciable !
@DorraBartaguiz

23. <<Interface>>
Price
+CalculateAmount()
FrenchPrice
-preTaxAmount
-tax
#CalculateVat()
#CalculatePreTaxAmount()
<<Abstract>>
BasePrice
+CalculateTotal()
#CalculateVat()
#CalculatePreTaxAmount()
LuxembourgishPrice
-preTaxServiceAmount
-serviceTax
-preTaxMaterialAmount
-materialTax
#CalculateVat()
#CalculatePreTaxAmount()
protected override double CalculateVat()
{
return preTaxAmount * tax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxAmount;
}
public double CalculateTotal()
{
return CalculateVat() + CalculatePreTaxAmount();
}
protected abstract double CalculateVat();
protected abstract double CalculatePreTaxAmount();
protected override double CalculateVat()
{
return preTaxServiceAmount * serviceTax +
preTaxMaterialAmount * materialTax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
Tester
unitairement les
sous calculs ?!
@DorraBartaguiz

24. <<Interface>>
Price
+CalculateAmount()
FrenchPrice
-preTaxAmount
-tax
#CalculateVat()
#CalculatePreTaxAmount()
<<Abstract>>
BasePrice
+CalculateTotal()
#CalculateVat()
#CalculatePreTaxAmount()
LuxembourgishPrice
-preTaxServiceAmount
-serviceTax
-preTaxMaterialAmount
-materialTax
#CalculateVat()
#CalculatePreTaxAmount()
protected override double CalculateVat()
{
return preTaxAmount * tax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxAmount;
}
public double CalculateTotal()
{
return CalculateVat() + CalculatePreTaxAmount();
}
protected abstract double CalculateVat();
protected abstract double CalculatePreTaxAmount();
protected override double CalculateVat()
{
return preTaxServiceAmount * serviceTax +
preTaxMaterialAmount * materialTax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
Le même test
se répète !
@DorraBartaguiz

25. Supprimer du code,
jamais de la vie !
On le garde au cas où !
@DorraBartaguiz

26. <<Interface>>
Price
+CalculateAmount()
FrenchPrice
-preTaxAmount
-tax
#CalculateVat()
#CalculatePreTaxAmount()
<<Abstract>>
BasePrice
+CalculateTotal()
#CalculateVat()
#CalculatePreTaxAmount()
LuxembourgishPrice
-preTaxServiceAmount
-serviceTax
-preTaxMaterialAmount
-materialTax
#CalculateVat()
#CalculatePreTaxAmount()
protected override double CalculateVat()
{
return preTaxAmount * tax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxAmount;
}
public double CalculateTotal()
{
return CalculateVat() + CalculatePreTaxAmount();
}
protected abstract double CalculateVat();
protected abstract double CalculatePreTaxAmount();
protected override double CalculateVat()
{
return preTaxServiceAmount * serviceTax +
preTaxMaterialAmount * materialTax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
Le même test
se répète !
@DorraBartaguiz

27. <<Interface>>
Price
+CalculateAmount()
FrenchPrice
-preTaxAmount
-tax
#CalculateVat()
#CalculatePreTaxAmount()
<<Abstract>>
BasePrice
+CalculateTotal()
#CalculateVat()
#CalculatePreTaxAmount()
LuxembourgishPrice
-preTaxServiceAmount
-serviceTax
-preTaxMaterialAmount
-materialTax
#CalculateVat()
#CalculatePreTaxAmount()
protected override double CalculateVat()
{
return preTaxAmount * tax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxAmount;
}
public double CalculateTotal()
{
return CalculateVat() + CalculatePreTaxAmount();
}
protected abstract double CalculateVat();
protected abstract double CalculatePreTaxAmount();
protected override double CalculateVat()
{
return preTaxServiceAmount * serviceTax +
preTaxMaterialAmount * materialTax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
Couplage
Dépendance
@DorraBartaguiz

28. USA
Tips = 10% du Total TTC
<<Interface>>
Price
+CalculateAmount()
FrenchPrice
-preTaxAmount
-tax
#CalculateVat()
#CalculatePreTaxAmount()
<<Abstract>>
BasePrice
+CalculateTotal()
#CalculateVat()
#CalculatePreTaxAmount()
LuxembourgishPrice
-preTaxServiceAmount
-serviceTax
-preTaxMaterialAmount
-materialTax
#CalculateVat()
#CalculatePreTaxAmount()
USAPrice
-preTaxAmount
-tax
#CalculateVat()
#CalculatePreTaxAmount()
protected override double CalculateVat()
{
return preTaxAmount * tax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxAmount;
}
public double CalculateTotal()
{
return CalculateVat() + CalculatePreTaxAmount();
}
protected abstract double CalculateVat();
protected abstract double CalculatePreTaxAmount();
protected override double CalculateVat()
{
return preTaxServiceAmount * serviceTax +
preTaxMaterialAmount * materialTax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
@DorraBartaguiz

29. <<Interface>>
Price
+CalculateAmount()
FrenchPrice
-preTaxAmount
-tax
#CalculateVat()
#CalculatePreTaxAmount()
<<Abstract>>
BasePrice
+CalculateTotal()
#CalculateVat()
#CalculatePreTaxAmount()
LuxembourgishPrice
-preTaxServiceAmount
-serviceTax
-preTaxMaterialAmount
-materialTax
#CalculateVat()
#CalculatePreTaxAmount()
USAPrice
-preTaxAmount
-tax
#CalculateVat()
#CalculatePreTaxAmount()
protected override double CalculateVat()
{
return preTaxAmount * tax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxAmount;
}
public double CalculateTotal()
{
if(this.GetType() == typeof(USAPrice))
{
var total = CalculateVat() + CalculatePreTaxAmount();
return total + total * 0.10;
}
return CalculateVat() + CalculatePreTaxAmount();
}
protected abstract double CalculateVat();
protected abstract double CalculatePreTaxAmount();
protected override double CalculateVat()
{
return preTaxServiceAmount * serviceTax +
preTaxMaterialAmount * materialTax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
@DorraBartaguiz

30. <<Interface>>
Price
+CalculateAmount()
FrenchPrice
-preTaxAmount
-tax
#CalculateVat()
#CalculatePreTaxAmount()
<<Abstract>>
BasePrice
+CalculateTotal()
#CalculateVat()
#CalculatePreTaxAmount()
LuxembourgishPrice
-preTaxServiceAmount
-serviceTax
-preTaxMaterialAmount
-materialTax
#CalculateVat()
#CalculatePreTaxAmount()
USAPrice
-preTaxAmount
-tax
#CalculateVat()
#CalculatePreTaxAmount()
protected override double CalculateVat()
{
return preTaxAmount * tax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxAmount;
}
public virtual double CalculateTotal()
{
return CalculateVat() + CalculatePreTaxAmount();
}
protected abstract double CalculateVat();
protected abstract double CalculatePreTaxAmount();
protected override double CalculateVat()
{
return preTaxServiceAmount * serviceTax +
preTaxMaterialAmount * materialTax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
public override double CalculateTotal()
{
var total = CalculateVat() + CalculatePreTaxAmount();
// var total = base.CalculateTotal();
return total + total * 0.10;
}
protected override double CalculateVat()
{
return preTaxAmount * tax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxAmount;
}
@DorraBartaguiz

31. SOLID
Principe de substitution de
Liskov
@DorraBartaguiz

32. Classe abstraite
Non
instanciable !
Le même test
se répète !
Couplage
Dépendance
@DorraBartaguiz

33. Les classes abstraites,
c’est fini !
(et c’est la faute à TDD)
@DorraBartaguiz

34. TDD
@DorraBartaguiz

35. Décomposition Exemples
Priorisation Baby steps
Prérequis
@DorraBartaguiz

36. Besoin du garagiste
• En France
• 150€ HT & 19.6% taxe
• Total : 179,4€ TTC
• Au Luxembourg
• 100€ HT de matériel & 15% taxe de matériel => total matériel : 115€
• 50€ HT de service & 12% taxe de service => total service : 56€
• Total : 171€
@DorraBartaguiz

37. Décomposer
@DorraBartaguiz

38. Identifier les composants
Somme HT et Taxe
Total hors taxe
Total
Calcul montant HT
France
Calcul montant HT
Luxembourg
Calcul taxe France
Calcul taxe Luxembourg
Total taxe
Calcul taxe
Calcul montant HT
Calcul Total
Montant hors taxe
Taxe
Montant hors taxe
Montant hors taxe service
Montant hors taxe matériel
Montant hors taxe service
Taxe service
Taxe matériel
Montant hors taxe matériel
@DorraBartaguiz

39. Identifier les composants
• Calcul du total
• Calcul du montant HT
• France
• Luxembourg
• Calcul de la taxe
• France
• Luxembourg
@DorraBartaguiz

40. Inside out
vs
Outside in
@DorraBartaguiz

41. Inside out
Classic approach Chicago school
Bottom up
@DorraBartaguiz

42. Inside out
Livre « Software Craft » - Edition Dunod
@DorraBartaguiz

43. Inside out
Somme HT et Taxe
Total hors taxe
Total
Calcul montant HT
France
Calcul montant HT
Luxembourg
Calcul taxe France
Calcul taxe Luxembourg
Total taxe
Calcul taxe
Calcul montant HT
Calcul Total
Montant hors taxe
Taxe
Montant hors taxe
Montant hors taxe service
Montant hors taxe matériel
Montant hors taxe service
Taxe service
Taxe matériel
Montant hors taxe matériel
@DorraBartaguiz

44. Outside in
Mockist approach London school
Top down
@DorraBartaguiz

45. Outside in
Livre « Software Craft » - Edition Dunod
@DorraBartaguiz

46. Outside in
Livre « Software Craft » - Edition Dunod
@DorraBartaguiz

47. Outside in
Livre « Software Craft » - Edition Dunod
@DorraBartaguiz

48. Outside in
Livre « Software Craft » - Edition Dunod
@DorraBartaguiz

49. Outside in
Livre « Software Craft » - Edition Dunod
@DorraBartaguiz

50. Outside in
Livre « Software Craft » - Edition Dunod
@DorraBartaguiz

51. Outside in
Somme HT et Taxe
Total hors taxe
Total
Calcul montant HT
France
Calcul montant HT
Luxembourg
Calcul taxe France
Calcul taxe Luxembourg
Total taxe
Calcul taxe
Calcul montant HT
Calcul Total
Montant hors taxe
Taxe
Montant hors taxe
Montant hors taxe service
Montant hors taxe matériel
Montant hors taxe service
Taxe service
Taxe matériel
Montant hors taxe matériel
@DorraBartaguiz

52. Inside out
vs
Outside in
@DorraBartaguiz

53. Inside out vs Outside in
Livre « Software Craft » - Edition Dunod
@DorraBartaguiz

54. Inside out
Somme HT et Taxe
Total hors taxe
Total
Calcul montant HT
France
Calcul montant HT
Luxembourg
Calcul taxe France
Calcul taxe Luxembourg
Total taxe
Calcul taxe
Calcul montant HT
Calcul Total
Montant hors taxe
Taxe
Montant hors taxe
Montant hors taxe service
Montant hors taxe matériel
Montant hors taxe service
Taxe service
Taxe matériel
Montant hors taxe matériel
@DorraBartaguiz

55. Trouver des exemples
@DorraBartaguiz

56. Bénéfices des exemples
Exemple
Besoin
attendu
Test
explicite
devient
vérifie
@DorraBartaguiz

57. Les exemples à consommer
sans modération
@DorraBartaguiz

58. Calcul montant HT
• 150 € => 150 €
• 10.5 € => 10.5 €
• 0 € => 0 €
• 100 €, 50 € => 150 €
• 100 €, 0 € => 100 €
• 10.5 €, 0 € => 10.5 €
• 0 €, 0 € => 0 €
Calcul montant HT
France
Montant hors taxe Montant hors taxe
Calcul montant HT
Luxembourg
Montant hors taxe service
Montant hors taxe matériel
Montant hors taxe
@DorraBartaguiz

59. Calcul montant HT
• 150 € => 150 €
• 10.5 € => 10.5 €
• 0 € => 0 €
• 100 €, 50 € => 150 €
• 100 €, 0 € => 100 €
• 10.5 €, 0 € => 10.5 €
• 0 €, 0 € => 0 €
Calcul montant HT
France
Montant hors taxe Montant hors taxe
Calcul montant HT
Luxembourg
Montant hors taxe service
Montant hors taxe matériel
Montant hors taxe
@DorraBartaguiz

60. Baby steps
L’art d’identifier des exemples pour avancer par petits pas
@DorraBartaguiz

61. Calcul montant HT
FrenchPrice
+FrenchPrice(double preTaxAmount)
-preTaxAmount
+CalculatePreTaxAmount()
LuxembourgishPrice
+LuxembourgishPrice(
double preTaxServiceAmount,
double preTaxMaterialAmount)
-preTaxServiceAmount
-preTaxMaterialAmount
+CalculatePreTaxAmount()
public double CalculatePreTaxAmount()
{
return preTaxAmount;
}
public double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
@DorraBartaguiz

62. Calcul taxe
• 150 €, 19.6% => 29.4 €
• 0 €, 19.6% => 0 €
• 100 €, 15%, 50 €, 12% => 21 €
• 100 €, 15%, 0 €, 12% => 15 €
• 0 €, 15%, 0 €, 12% => 0 €
Montant taxe
Calcul taxe France
Taxe
Montant hors taxe
Calcul taxe
Luxembourg
Montant taxe
Montant hors taxe service
Taxe service
Taxe matériel
Montant hors taxe matériel
@DorraBartaguiz

63. Calcul taxe
• 150 €, 19.6% => 29.4 €
• 0 €, 19.6% => 0 €
• 100 €, 15%, 50 €, 12% => 21 €
• 100 €, 15%, 0 €, 12% => 15 €
• 0 €, 15%, 0 €, 12% => 0 €
Montant taxe
Calcul taxe France
Taxe
Montant hors taxe
Calcul taxe
Luxembourg
Montant taxe
Montant hors taxe service
Taxe service
Taxe matériel
Montant hors taxe matériel
@DorraBartaguiz

64. Calcul taxe
• 150 €, 19.6% => 29.4 €
• 0 €, 19.6% => 0 €
• 100 €, 15%, 50 €, 12% => 21 €
• 100 €, 15%, 0 €, 12% => 15 €
• 0 €, 15%, 0 €, 12% => 0 €
Montant taxe
Calcul taxe France
Taxe
Montant hors taxe
Calcul taxe
Luxembourg
Montant taxe
Montant hors taxe service
Taxe service
Taxe matériel
Montant hors taxe matériel
@DorraBartaguiz

65. Calcul taxe
• 0 €, 19.6% => 0 € • 0 €, 15%, 0 €, 12% => 0 €
FrenchPrice
+FrenchPrice(
double preTaxAmount,
double tax)
-preTaxAmount
-tax
+CalculatePreTaxAmount()
+CalculateVat()
public double CalculatePreTaxAmount()
{
return preTaxAmount;
}
public double CalculateVat()
{
return preTaxAmount;
}
LuxembourgishPrice
+LuxembourgishPrice(double preTaxServiceAmount,
double preTaxMaterialAmount,
double serviceTax, double materialTax)
-preTaxServiceAmount
-preTaxMaterialAmount
-serviceTax
-materialTax
+CalculatePreTaxAmount()
+CalculateVat()
public double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
public double CalculateVat()
{
return preTaxServiceAmount;
}
@DorraBartaguiz

66. Calcul taxe
• 150 €, 19.6% => 29.4 € • 100 €, 15%, 0 €, 12% => 15 €
FrenchPrice
+FrenchPrice(
double preTaxAmount,
double tax)
-preTaxAmount
-tax
+CalculatePreTaxAmount()
+CalculateVat()
public double CalculatePreTaxAmount()
{
return preTaxAmount;
}
public double CalculateVat()
{
return preTaxAmount * tax;
}
LuxembourgishPrice
+LuxembourgishPrice(double preTaxServiceAmount,
double preTaxMaterialAmount,
double serviceTax, double materialTax)
-preTaxServiceAmount
-preTaxMaterialAmount
-serviceTax
-materialTax
+CalculatePreTaxAmount()
+CalculateVat()
public double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
public double CalculateVat()
{
return preTaxServiceAmount * serviceTax;
}
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67. Calcul taxe
• 150 €, 19.6% => 29.4 € • 100 €, 15%, 50 €, 12% => 21 €
FrenchPrice
+FrenchPrice(
double preTaxAmount,
double tax)
-preTaxAmount
-tax
+CalculatePreTaxAmount()
+CalculateVat()
public double CalculatePreTaxAmount()
{
return preTaxAmount;
}
public double CalculateVat()
{
return preTaxAmount * tax;
}
LuxembourgishPrice
+LuxembourgishPrice(double preTaxServiceAmount,
double preTaxMaterialAmount,
double serviceTax, double materialTax)
-preTaxServiceAmount
-preTaxMaterialAmount
-serviceTax
-materialTax
+CalculatePreTaxAmount()
+CalculateVat()
public double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
public double CalculateVat()
{
return preTaxServiceAmount * serviceTax
+ preTaxMaterialAmount * materialTax;
}
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68. Somme HT et taxe
• 150 €, 29.4 € => 179.4 €
• 150 €, 0 € => 150 €
Somme HT et Taxe
Total hors taxe Total
Total taxe
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69. Somme HT et taxe
• 150 €, 29.4 € => 179.4 €
• 150 €, 0 € => 150 €
TotalCalculator
+CalculateTotal(double preTaxAmount, double taxAmount)
public double CalculateTotal(double preTaxAmount,
double taxAmount)
{
return preTaxAmount + taxAmount;
}
Somme HT et Taxe
Total hors taxe Total
Total taxe
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70. Côté appelant
public void CalculateTotalPrice()
{
var preTaxServiceAmount = 50;
var serviceTax = 0.12;
var preTaxMaterialAmount = 100;
var materialTax = 0.15;
var luxembourgishPrice = new LuxembourgishPrice(preTaxServiceAmount, serviceTax,
preTaxMaterialAmount, materialTax);
var preTaxAmount = luxembourgishPrice.CalculatePreTaxAmount();
var taxAmount = luxembourgishPrice.CalculateVat();
var totalCalculator = new TotalCalculator();
var total = totalCalculator.CalculateTotal(preTaxAmount, taxAmount);
Check.That(total).IsEqualTo(171);
}
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71. Simplifier l’appelant
public void CalculateTotalPrice_For_Luxembourg()
{
var preTaxServiceAmount = 50;
var serviceTax = 0.12;
var preTaxMaterialAmount = 100;
var materialTax = 0.15;
var luxembourgishPrice = new LuxembourgishPrice(preTaxServiceAmount, serviceTax,
preTaxMaterialAmount, materialTax);
var totalCalculator = new TotalCalculator(luxembourgishPrice);
var totalCalculator.CalculateTotal();
Check.That(total).IsEqualTo(171);
}
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72. Simplifier l’appelant
public void CalculateTotalPrice_For_France()
{
var preTaxAmount = 150;
var tax = 0.196;
var frenchPrice = new FrenchPrice(preTaxAmount, tax);
var totalCalculator = new TotalCalculator(frenchPrice);
var totalCalculator.CalculateTotal();
Check.That(total).IsEqualTo(179.4);
}
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73. Interface
FrenchPrice
+FrenchPrice(
double preTaxAmount,
double tax)
-preTaxAmount
-tax
+CalculatePreTaxAmount()
+CalculateVat()
LuxembourgishPrice
+LuxembourgishPrice(double preTaxServiceAmount,
double preTaxMaterialAmount,
double serviceTax, double materialTax)
-preTaxServiceAmount
-preTaxMaterialAmount
-serviceTax
-materialTax
+CalculatePreTaxAmount()
+CalculateVat()
<<Interface>>
Price
+CalculatePreTaxAmount()
+CalculateVat()
public double CalculatePreTaxAmount()
{
return preTaxAmount;
}
public double CalculateVat()
{
return preTaxAmount * tax;
}
public double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
public double CalculateVat()
{
return preTaxServiceAmount * serviceTax
+ preTaxMaterialAmount * materialTax;
}
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74. Composition
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75. Pas de composition
TotalCalculator
+CalculateTotal(double preTaxAmount, double taxAmount)
public double CalculateTotal(double preTaxAmount,
double taxAmount)
{
return preTaxAmount + taxAmount;
}
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76. Composition
TotalCalculator
+TotalCalculator(Price price)
-Price price
+CalculateTotal()
public double CalculateTotal()
{
return price.CalculatePreTaxAmount() +
price.CalculateVat();
}
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77. Composition
FrenchPrice
+FrenchPrice(
double preTaxAmount,
double tax)
-preTaxAmount
-tax
+CalculatePreTaxAmount()
+CalculateVat()
LuxembourgishPrice
+LuxembourgishPrice(double preTaxServiceAmount,
double preTaxMaterialAmount,
double serviceTax, double materialTax)
-preTaxServiceAmount
-preTaxMaterialAmount
-serviceTax
-materialTax
+CalculatePreTaxAmount()
+CalculateVat()
<<Interface>>
Price
+CalculatePreTaxAmount()
+CalculateVat()
TotalCalculator
+TotalCalculator(Price price)
-Price price
+CalculateTotal()
use
public double CalculatePreTaxAmount()
{
return preTaxAmount;
}
public double CalculateVat()
{
return preTaxAmount * tax;
}
public double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
public double CalculateVat()
{
return preTaxServiceAmount * serviceTax
+ preTaxMaterialAmount * materialTax;
}
public double CalculateTotal()
{
return price.CalculatePreTaxAmount() +
price.CalculateVat();
}
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78. <<Interface>>
Price
+CalculateAmount()
FrenchPrice
-preTaxAmount
-tax
#CalculateVat()
#CalculatePreTaxAmount()
<<Abstract>>
BasePrice
+CalculateTotal()
#CalculateVat()
#CalculatePreTaxAmount()
LuxembourgishPrice
-preTaxServiceAmount
-serviceTax
-preTaxMaterialAmount
-materialTax
#CalculateVat()
#CalculatePreTaxAmount()
protected override double CalculateVat()
{
return preTaxAmount * tax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxAmount;
}
public double CalculateTotal()
{
return CalculateVat() + CalculatePreTaxAmount();
}
protected abstract double CalculateVat();
protected abstract double CalculatePreTaxAmount();
protected override double CalculateVat()
{
return preTaxServiceAmount * serviceTax +
preTaxMaterialAmount * materialTax;
}
protected override double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
Non instanciable
Le même test se répète
Couplage
Dépendance
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79. FrenchPrice
+FrenchPrice(
double preTaxAmount,
double tax)
-preTaxAmount
-tax
+CalculatePreTaxAmount()
+CalculateVat()
LuxembourgishPrice
+LuxembourgishPrice(double preTaxServiceAmount,
double preTaxMaterialAmount,
double serviceTax, double materialTax)
-preTaxServiceAmount
-preTaxMaterialAmount
-serviceTax
-materialTax
+CalculatePreTaxAmount()
+CalculateVat()
<<Interface>>
Price
+CalculatePreTaxAmount()
+CalculateVat()
TotalCalculator
+TotalCalculator(Price price)
-Price price
+CalculateTotal()
use
public double CalculatePreTaxAmount()
{
return preTaxAmount;
}
public double CalculateVat()
{
return preTaxAmount * tax;
}
public double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
public double CalculateVat()
{
return preTaxServiceAmount * serviceTax
+ preTaxMaterialAmount * materialTax;
}
public double CalculateTotal()
{
return price.CalculatePreTaxAmount() +
price.CalculateVat();
}
Tout est instanciable
Pas de test qui se répète
Dépendance inversée
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80. Pourboires = Total TTC + 10%
FrenchPrice
+FrenchPrice(
double preTaxAmount,
double tax)
-preTaxAmount
-tax
+CalculatePreTaxAmount()
+CalculateVat()
LuxembourgishPrice
+LuxembourgishPrice(double preTaxServiceAmount,
double preTaxMaterialAmount,
double serviceTax, double materialTax)
-preTaxServiceAmount
-preTaxMaterialAmount
-serviceTax
-materialTax
+CalculatePreTaxAmount()
+CalculateVat()
<<Interface>>
Price
+CalculatePreTaxAmount()
+CalculateVat()
DefaultTotalCalculator
+DefaultTotalCalculator(Price price)
-price
+CalculateTotal()
USAPrice
-preTaxAmount
-tax
#CalculateVat()
#CalculatePreTaxAmount()
<<Interface>>
TotalCalculator
+CalculateTotal()
TotalCalculatorWithTips
+TotalCalculatorWithTips(Price price)
-price
-tips
+CalculateTotal()
public double CalculatePreTaxAmount()
{
return preTaxAmount;
}
public double CalculateVat()
{
return preTaxAmount * tax;
}
public double CalculatePreTaxAmount()
{
return preTaxServiceAmount +
preTaxMaterialAmount;
}
public double CalculateVat()
{
return preTaxServiceAmount * serviceTax
+ preTaxMaterialAmount * materialTax;
}
public double CalculateTotal()
{
return price.CalculatePreTaxAmount() +
price.CalculateVat();
}
public double CalculateTotal()
{
var total = price.CalculatePreTaxAmount() +
price.CalculateVat();
return total + total * tips;
}
@DorraBartaguiz

81. Composition
over
Inheritance
« Design Patterns: Elements of Reusable Object-Oriented Software »
écrit par Erich Gamma, Richard Helm, Ralph Johnson, et John Vlissides,
avec une préface de Grady Booch
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82. Composition
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Make big things from small things in the same way.
That’s the power of composition.
Scott Wlaschin

83. Les classes abstraites,
c’est fini !
(et c’est la faute à TDD)
Baby steps Composition
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84. Buy the book!
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85. Merci !
https://roti.express/r/alp-19
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