Slides from my talk at Dutch PHP Conference in Amsterdam More Domain-Driven Design related content at: https://domaincentric.net/

1. PHPSpecthe only Design Tool you need
flickr.com/dad/5528226004

2. Kacper Gunia @cakper
Software Engineer @SensioLabsUK
Symfony Certified Developer
PHPers Silesia @PHPersPL

3. !
‘Is my code well
designed?’

4. ’That’s not the way
I would have done it…’

5. It’s hard to
change!

6. It’s hard to
change!Rigidity

7. We're afraid
to change it…

8. We're
to change itFragility

9. We cannot
reuse it!

10. We cannot
reuse it!Immobility

13. What is
Design
about?

14. ‘The key in making great and
growable systems is much more to
design how its
modules communicate
rather than what their internal
properties and behaviors should be.’
Alan Kay

15. Design is about
Messaging

16. $orders
=
$orderRepository
-­‐>getEntityManager()
-­‐>createOrderQuery($customer)
-­‐>execute();

17. $orders
=
$orderRepository
-­‐>findBy($customer);
!

18. We have
to refactor! :)

19. We need
two weeks
to refactor! :)

20. We need
two sprints
to refactor! :|

21. We need
two months
to refactor! :/

22. Refactoring
is the process of restructuring
existing code without
changing its external behavior

23. 4 Rules of Simple Design
1. Passes its tests
2. Minimizes duplication
3. Maximizes clarity
4. Has fewer elements

24. …so we need
to write
Tests!

25. how
to write
Tests?

26. Tests
Driven
Development

27. Red
GreenRefactor

28. Red
GreenRefactor

29. But!

30. How to test
something that
doesn’t exist?
flickr.com/ucumari/580865728/

31. Test in TDD
means
specification

32. Specification
describes
behavior

33. Behavior
Driven
Development

34. BDD improves
Naming
Conventions
Tools

35. Story BDD
vs
Spec BDD

36. Story BDD
description of
business-targeted
application behavior

37. Spec BDD
specification for
low-level
implementation

38. http://phpspec.net/

39. Spec BDD
tool created by
@_md & @everzet

40. Bundled with
mocking library
Prophecy

41. But!

42. Isn’t it a tool just
like PHPUnit?

43. PHPUnit is a
Testing Tool

44. PHPSpec is the
Design Tool

46. class
CustomerRepositoryTest
extends
PHPUnit_Framework_TestCase
{
function
testFindCustomerById()
{
$customerRepository
=
new
CustomerRepository;
!
$customer
=
$customerRepository-­‐>findById(5);
$this-­‐>assertInstanceOf('Customer',
$customer);
}
}

49. class
CustomerRepositorySpec
extends
ObjectBehavior
{
function
it_is_initializable()
{
$this-­‐>shouldHaveType('CustomerRepository');
}
}

50. Naming

51. TestCase
!
Specification

52. Test
!
Example

53. Assertion
!
Expectation

54. OK, so how to
specify a method?

55. What method can do?
return a value
modify state
delegate
throw an exception

56. Command-Query
Separation

57. Command
change the state of a system
but do not return a value

58. Query
return a result and do not
change the state of the
system (free of side effects)

59. Never both!

65. class
CustomerRepositorySpec
extends
ObjectBehavior
{
function
it_loads_user_preferences()
{
$customer
=
$this-­‐>findById(5);
!
$customer-­‐>shouldBeAnInstanceOf('Customer');
}
}

66. Matchers

67. Type
shouldBeAnInstanceOf(*)
shouldReturnAnInstanceOf(*)
shouldHaveType(*)

68. $customer-­‐>shouldBeAnInstanceOf('Customer');

69. Identity ===
shouldReturn(*)
shouldBe(*)
shouldEqual(*)
shouldBeEqualTo(*)

70. $this-­‐>findById(-­‐1)-­‐>shouldReturn(null);

71. Comparison ==
shouldBeLike(*)

72. $this-­‐>getAmount()-­‐>shouldBeLike(5);

73. Throw
throw(*)->during*()

74. $this-­‐>shouldThrow(‘InvalidArgumentException’)
-­‐>duringFindByCustomer(null);

75. Object State
shouldHave*()

76. $car-­‐>hasEngine();
!
$this-­‐>shouldHaveEngine();

77. Scalar
shouldBeString()
shouldBeArray()

78. Count
shouldHaveCount(*)

79. Or write your own
Inline Matcher

80. function
it_should_have_holland_as_avialable_country()
{
$this-­‐>getCountryCodes()-­‐>shouldHaveValue('NL');
}
!
public
function
getMatchers()
{
return
[
'haveValue'
=>
function
($subject,
$value)
{
return
in_array($value,
$subject);
}
];
}

81. But!

82. Design is about
Messaging!

83. And (so far) there
is no messaging…

84. London School

85. Mockist TDD
only tested object is real

86. Test Doubles

87. Dummy
tested code requires
parameter but
doesn’t need to use it

88. function
let(EntityManager
$entityManager)
{
$this-­‐>beConstructedWith($entityManager);
}
!
function
it_returns_customer_by_id()
{
$customer
=
$this-­‐>findById(5);
!
$customer-­‐>shouldBeAnInstanceOf('Customer');
}
}

89. function
let(EntityManager
$entityManager)
{
$this-­‐>beConstructedWith($entityManager);
}
!
function
it_returns_customer_by_id()
{
$customer
=
$this-­‐>findById(5);
!
$customer-­‐>shouldBeAnInstanceOf('Customer');
}
}

90. Stub
provides "indirect input"
to the tested code

91. function
it_bolds_the_output(Stream
$stream)
{
$stream-­‐>getOutput()
-­‐>willReturn('DPC');
!
$this-­‐>bold($stream)
-­‐>shouldReturn('<b>DPC</b>’);
}

92. function
it_bolds_the_output(Stream
$stream)
{
$stream-­‐>getOutput()
-­‐>willReturn('DPC');
!
$this-­‐>bold($stream)
-­‐>shouldReturn('<b>DPC</b>’);
}

93. Mocks
verifies "indirect output”
of the tested code

94. function
let(Logger
$logger)
{
$this-­‐>beConstructedWith($logger);
}
!
function
it_returns_customer_by_id(Logger
$logger)
{
$logger-­‐>debug('DB
queried')
-­‐>shouldBeCalled();
!
$this-­‐>findById(5);
}

95. function
let(Logger
$logger)
{
$this-­‐>beConstructedWith($logger);
}
!
function
it_returns_customer_by_id(Logger
$logger)
{
$logger-­‐>debug('DB
queried')
-­‐>shouldBeCalled();
!
$this-­‐>findById(5);
}

96. Spy
verifies "indirect output”
by asserting the expectations
afterwards

97. function
let(Logger
$logger)
{
$this-­‐>beConstructedWith($logger);
}
!
function
it_returns_customer_by_id(Logger
$logger)
{
$this-­‐>findById(5);
!
$logger-­‐>debug('DB
queried')
-­‐>shouldHaveBeenCalled();
}

98. function
let(Logger
$logger)
{
$this-­‐>beConstructedWith($logger);
}
!
function
it_returns_customer_by_id(Logger
$logger)
{
$this-­‐>findById(5);
!
$logger-­‐>debug('DB
queried')
-­‐>shouldHaveBeenCalled();
}

99. (a bit more)
complex example

100. function
let(SecurityContext
$securityContext)
{
$this-­‐>beConstructedWith($securityContext);
}
!
function
it_loads_user_preferences(
GetResponseEvent
$event,
SecurityContext
$securityContext,
TokenInterface
$token,
User
$user)
{
$securityContext-­‐>getToken()-­‐>willReturn($token);
$token-­‐>getUser()-­‐>willReturn($user);
!
$user-­‐>setPreferences(Argument::type('Preferences'))
-­‐>shouldBeCalled();
!
$this-­‐>handle($event);
}

101. function
let(SecurityContext
$securityContext)
{
$this-­‐>beConstructedWith($securityContext);
}
!
function
it_loads_user_preferences(
GetResponseEvent
$event,
SecurityContext
$securityContext,
TokenInterface
$token,
User
$user)
{
$securityContext-­‐>getToken()-­‐>willReturn($token);
$token-­‐>getUser()-­‐>willReturn($user);
!
$user-­‐>setPreferences(Argument::type('Preferences'))
-­‐>shouldBeCalled();
!
$this-­‐>handle($event);
}

102. function
let(SecurityContext
$securityContext)
{
$this-­‐>beConstructedWith($securityContext);
}
!
function
it_loads_user_preferences(
GetResponseEvent
$event,
SecurityContext
$securityContext,
TokenInterface
$token,
User
$user)
{
$securityContext-­‐>getToken()-­‐>willReturn($token);
$token-­‐>getUser()-­‐>willReturn($user);
!
$user-­‐>setPreferences(Argument::type('Preferences'))
-­‐>shouldBeCalled();
!
$this-­‐>handle($event);
}

103. function
let(SecurityContext
$securityContext)
{
$this-­‐>beConstructedWith($securityContext);
}
!
function
it_loads_user_preferences(
GetResponseEvent
$event,
SecurityContext
$securityContext,
TokenInterface
$token,
User
$user)
{
$securityContext-­‐>getToken()-­‐>willReturn($token);
$token-­‐>getUser()-­‐>willReturn($user);
!
$user-­‐>setPreferences(Argument::type('Preferences'))
-­‐>shouldBeCalled();
!
$this-­‐>handle($event);
}

104. function
let(SecurityContext
$securityContext)
{
$this-­‐>beConstructedWith($securityContext);
}
!
function
it_loads_user_preferences(
GetResponseEvent
$event,
SecurityContext
$securityContext,
TokenInterface
$token,
User
$user)
{
$securityContext-­‐>getToken()-­‐>willReturn($token);
$token-­‐>getUser()-­‐>willReturn($user);
!
$user-­‐>setPreferences(Argument::type('Preferences'))
-­‐>shouldBeCalled();
!
$this-­‐>handle($event);
}

105. But mocking
becomes painful…

106. And it smells…

107. Law of Demeter
unit should only
talk to its friends;
don't talk to strangers

108. It’s time to
refactor! :)

109. function
it_loads_user_preferences(
GetResponseEvent
$event,
SecurityContext
$securityContext,
TokenInterface
$token,
User
$user)
{
$securityContext-­‐>getToken()-­‐>willReturn($token);
$token-­‐>getUser()-­‐>willReturn($user);
!
$user-­‐>setPreferences(Argument::type('Preferences'))
-­‐>shouldBeCalled();
!
$this-­‐>handle($event);
}

110. function
it_returns_user_from_token(
SecurityContext
$securityContext,
TokenInterface
$token,
User
$user)
{
$securityContext-­‐>getToken()-­‐>willReturn($token);
$token-­‐>getUser()-­‐>willReturn($user);
!
$this-­‐>getUser()-­‐>shouldReturn($user);
}
!

111. public
function
__construct(SecurityContext
$securityContext){
$this-­‐>securityContext
=
$securityContext;
}
!
public
function
getUser()
{
$token
=
$this-­‐>securityContext-­‐>getToken();
if
($token
instanceof
TokenInterface)
{
return
$token-­‐>getUser();
}
!
return
null;
}

112. function
it_loads_user_preferences(
GetResponseEvent
$event,
SecurityContext
$securityContext,
TokenInterface
$token,
User
$user)
{
$securityContext-­‐>getToken()-­‐>willReturn($token);
$token-­‐>getUser()-­‐>willReturn($user);
!
$user-­‐>setPreferences(Argument::type('Preferences'))
-­‐>shouldBeCalled();
!
$this-­‐>handle($event);
}

113. function
it_loads_user_preferences(
GetResponseEvent
$event,
DomainSecurityContext
$securityContext,
User
$user)
{
$securityContext-­‐>getUser()-­‐>willReturn($user);
!
$user-­‐>setPreferences(Argument::type(‘Preferences'))
-­‐>shouldBeCalled();
!
$this-­‐>handle($event);
}

114. Composition over Inheritance
separation of concerns
small, well focused objects
composition is simpler to test

115. public
function
__construct(SecurityContext
$securityContext){
$this-­‐>securityContext
=
$securityContext;
}
!
public
function
getUser()
{
$token
=
$this-­‐>securityContext-­‐>getToken();
if
($token
instanceof
TokenInterface)
{
return
$token-­‐>getUser();
}
!
return
null;
}

116. We can still
improve

117. function
it_loads_user_preferences(
GetResponseEvent
$event,
DomainSecurityContext
$securityContext,
User
$user)
{
$securityContext-­‐>getUser()-­‐>willReturn($user);
!
$user-­‐>setPreferences(Argument::type(‘Preferences'))
-­‐>shouldBeCalled();
!
$this-­‐>handle($event);
}

118. function
it_loads_user_preferences(
GetResponseEvent
$event,
DomainSecurityContextInterface
$securityContext,
User
$user)
{
$securityContext-­‐>getUser()-­‐>willReturn($user);
!
$user-­‐>setPreferences(Argument::type(‘Preferences'))
-­‐>shouldBeCalled();
!
$this-­‐>handle($event);
}

119. Dependency
Inversion Principle

120. high-level modules should
not depend on low-level
modules; both should depend
on abstractions
DIP states:

121. DIP states:
abstractions should not
depend upon details; details
should depend upon
abstractions

124. Isn’t it overhead?

126. What are benefits of
using PHPSpec?

127. TDD-cycle
oriented tool

128. ease Mocking

129. focused on
Messaging

130. encourages
injecting right
Collaborators

131. and following
Law of Demeter

132. enables
Refactoring

133. and gives you
Regression Safety

134. and it’s trendy ;)

135. Is PHPSpec
the only design tool
we need?

136. s

138. So it helps ;)

139. Kacper Gunia
Software Engineer
Symfony Certified Developer
PHPers Silesia
Thanks!

140. joind.in/10864