Slides from my talk at 4Developers conference in Warsaw More Domain-Driven Design related content at: https://domaincentric.net/

1. PHPSpec
the only Design Tool you need
flickr.com/mobilestreetlife/4179063482/

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. We're afraid
to change it…

7. We cannot
reuse it!

8. So what
Design
is about?

9. ‘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

10. Design is about
Messaging

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

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

13. We have
to refactor! :)

14. We need
two weeks
to refactor! :)

15. We need
two sprints
to refactor! :|

16. We need
two months
to refactor! :/

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

18. 4 Rules of Simple Design
1. Passes its tests
2. Minimizes duplication
3. Maximizes clarity
4. Has fewer elements

19. …so we need
to write
Tests!

20. how
to write
Tests?

21. Tests
Driven
Development

22. Red
GreenRefactor

23. Red
GreenRefactor

24. But!

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

26. Test in TDD
means
specification

27. Specification
describes
behavior

28. Behavior
Driven
Development

29. BDD improves
Naming
Conventions
Tools

30. Story BDD
vs
Spec BDD

31. Story BDD
description of
business-targeted
application behavior

32. Spec BDD
specification for
low-level
implementation

33. http://phpspec.net/

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

35. Bundled with
mocking library
Prophecy

36. composer
create-­‐project
cakper/phpspec-­‐standard
project-­‐name

37. But!

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

39. PHPUnit is a
Testing Tool

40. PHPSpec is the
Design Tool

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

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

47. Naming

48. TestCase
!
Specification

49. Test
!
Example

50. Assertion
!
Expectation

51. OK, so how to
specify a method?

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

53. Command-Query
Separation

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

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

56. Never both!

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

64. Matchers

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

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

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

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

69. Comparison ==
shouldBeLike(*)

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

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

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

73. Object State
shouldHave*()

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

75. Scalar
shouldBeString()
shouldBeArray()

76. Count
shouldHaveCount(*)

77. Or write your own
Inline Matcher

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

79. But!

80. Design is about
Messaging!

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

82. London School

83. Mockist TDD
only tested object is real

84. Test Doubles

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

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

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

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

89. function
it_bolds_the_output(Stream
$stream)
{
$stream-­‐>getOutput()
-­‐>willReturn('4
Developers');
!
$this-­‐>bold($stream)
-­‐>shouldReturn('<b>4
Developers</b>’);
}

90. function
it_bolds_the_output(Stream
$stream)
{
$stream-­‐>getOutput()
-­‐>willReturn('4
Developers');
!
$this-­‐>bold($stream)
-­‐>shouldReturn('<b>4
Developers</b>’);
}

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

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

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

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

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

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

97. (a bit more)
complex example

98. 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);
}

99. 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);
}

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. But mocking
becomes painful…

104. And it smells…

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

106. It’s time to
refactor! :)

107. 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);
}

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

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

110. 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);
}

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

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

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

114. We can still
improve

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

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

117. Dependency
Inversion Principle

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

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

122. Isn’t it overhead?

124. What are benefits of
using PHPSpec?

125. TDD-cycle
oriented tool

126. ease Mocking

127. focused on
Messaging

128. encourage
injecting right
Collaborators

129. and following
Demeter Low

130. enables
Refactoring

131. and gives you
Regression Safety

132. and it’s trendy ;)

133. Is PHPSpec
the only design tool
we need?

134. s

136. So it helps ;)

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