when to mock · when to mock @stuherbert $ git clone git@github.com:foo/bar.git $ cd bar $ composer...
Post on 04-Jul-2020
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@stuherbert
When To Mock
@stuherbert
Introductions
When To Mock
@stuherbert
of Unit TestingThe Holy Grail
When To Mock
@stuherbertWhen To Mock
$ git clone git@github.com:foo/bar.git $ cd bar $ composer install $ phpunit
@stuherbertWhen To Mock
$ git clone git@github.com:foo/bar.git $ cd bar $ composer install $ phpunit
@stuherbertWhen To Mock
$ git clone git@github.com:foo/bar.git $ cd bar $ composer install $ phpunit
@stuherbertWhen To Mock
$ git clone git@github.com:foo/bar.git $ cd bar $ composer install $ phpunit
@stuherbert
Unit TestsShould Execute Straight Out Of The Box
When To Mock
@stuherbert
This Was EasyIn The Pre-Web World
When To Mock
@stuherbert
• Our code wasn’t networked
• Our code used embedded data storage engines
• Our code wasn’t multi-user
When To Mock
@stuherbert
• Our code wasn’t networked
• Our code used embedded data storage engines
• Our code wasn’t multi-user
When To Mock
@stuherbert
• Our code wasn’t networked
• Our code used embedded data storage engines
• Our code wasn’t multi-user
When To Mock
@stuherbert
Self-ContainedOur Code Was
When To Mock
@stuherbert
Pre-Web Architecture Diagram
When To Mock
@stuherbert
Pre-Web Architecture Diagram
When To Mock
@stuherbert
Pre-Web Architecture Diagram
When To Mock
Application Stack
@stuherbert
Talks To ThingsToday’s Code
When To Mock
@stuherbert
Self ContainedToday’s Code Is Anything But
When To Mock
@stuherbert
Our Code Has Evolved From This
When To Mock
Application Stack
@stuherbert
Our Code Now Looks Like This
When To Mock
Database
Cache1
2
3
Internal Services
External Services
Controller Models
Views
Framework
LibrariesLibrariesLibraries
@stuherbert
Internally, More Complexity
When To Mock
Database
Cache1
2
3
Internal Services
External Services
Controller Models
Views
Framework
Libraries
@stuherbert
Internally, More Dependencies
When To Mock
Database
Cache1
2
3
Internal Services
External Services
Controller Models
Views
Framework
LibrariesLibrariesLibraries
@stuherbert
Storage Is Now A Service
When To Mock
Database
Cache1
2
3
Internal Services
External Services
Controller Models
Views
Framework
LibrariesLibrariesLibraries
@stuherbert
Functionality Is Now A Service
When To Mock
Database
Cache1
2
3
Internal Services
External Services
Controller Models
Views
Framework
LibrariesLibrariesLibraries
@stuherbert
Apps Are Now A Service To Users
When To Mock
Database
Cache1
2
3
Internal Services
External Services
Controller Models
Views
Framework
LibrariesLibrariesLibraries
@stuherbert
Unit TestsShould Execute Straight Out Of The Box
When To Mock
@stuherbert
Good Advice?Is This Still
When To Mock
@stuherbert
Still Good Advice?
• Makes testing reproducible
• Ease of use by new project members
• Supports continuous integration
When To Mock
@stuherbert
Still Good Advice?
• Makes testing reproducible
• Ease of use by new project members
• Supports continuous integration
When To Mock
@stuherbert
Still Good Advice?
• Makes testing reproducible
• Ease of use by new project members
• Supports continuous integration
When To Mock
@stuherbert
Unit TestsShould Execute Straight Out Of The Box
When To Mock
✓
@stuherbert
Now Requires HelpMaking Unit Tests Execute Out Of The Box
When To Mock
@stuherbert
We Want To Unit Test Like This
When To Mock
Application Stack
@stuherbert
Are GoneBut Those Days
When To Mock
@stuherbert
Our App Now Needs These
When To Mock
Database
Cache
Internal Services
External Services
@stuherbert
If We Mock These
When To Mock
Database
Cache
Internal Services
External Services
@stuherbert
We Can Unit Test Without Them
When To Mock
Database
Cache
Internal Services
External Services
@stuherbert
& We Can Simulate Failure Too
When To Mock
Database
Cache
Internal Services
External Services
@stuherbert
Three Key Questions
When To Mock
@stuherbert
• Can we mock all the things?
• Should we mock all the things?
• Should we mock inside our app?
When To Mock
@stuherbert
• Can we mock all the things?
• Should we mock all the things?
• Should we mock inside our app?
When To Mock
@stuherbert
• Can we mock all the things?
• Should we mock all the things?
• Should we mock inside our app?
When To Mock
@stuherbert
All The Things?Can We Mock
When To Mock
@stuherbert
• Given enough time and effort, yes we can
When To Mock
@stuherbert
All The Things?Should We Mock
When To Mock
@stuherbert
• Who is going to build the mocks?
• How do you prove your mock behaves accurately today?
• How do you prove your mock still behaves accurately tomorrow?
When To Mock
@stuherbert
• Who is going to build the mocks?
• How do you prove your mock behaves accurately today?
• How do you prove your mock still behaves accurately tomorrow?
When To Mock
@stuherbert
• Who is going to build the mocks?
• How do you prove your mock behaves accurately today?
• How do you prove your mock still behaves accurately tomorrow?
When To Mock
@stuherbert
• A mock can only be as good as the author’s understanding of whatever is being mocked
• Tests using rotted mocks will continue to pass, but the code will fail when shipped
When To Mock
@stuherbert
• A mock can only be as good as the author’s understanding of whatever is being mocked
• Tests using rotted mocks will continue to pass, but the code will fail when shipped
When To Mock
@stuherbert
Test what we can,
mock what we have to
When To Mock
@stuherbert
Inside Our App?Should We Mock
When To Mock
@stuherbert
Our Code?What Happens Inside
When To Mock
@stuherbert
• computation
• branching
• input / output
When To Mock
@stuherbert
• computation
• branching
• input / output
When To Mock
@stuherbert
• computation
• branching
• input / output
When To Mock
@stuherbert
Forming Execution Paths
When To Mock
@stuherbert
One Execution PathEach Unit Test Exercises
When To Mock
@stuherbert
Such As This
When To Mock
@stuherbert
Or This
When To Mock
@stuherbert
Or This
When To Mock
@stuherbert
The Code You Call?What Happens When You Mock
When To Mock
@stuherbert
Adding MocksShortens The Paths We Can Test
When To Mock
@stuherbert
Take A Code Path
When To Mock
@stuherbert
Inject A Mock
When To Mock
@stuherbert
Shorter Code Path
When To Mock
@stuherbert
Behind The Mock?But What About The Code
When To Mock
@stuherbert
?
Unreachable Code
When To Mock
?
?
?
@stuherbert
Unreachable CodeMocks Inside Your App Create
When To Mock
@stuherbert
Is Untestable CodeUnreachable Code
When To Mock
@stuherbert
What Is The RiskFrom The Code That You Can’t Test?
When To Mock
@stuherbert
Key Questions
• How do you prove your mock behaves accurately today?
• How do you prove your mock still behaves accurately tomorrow?
When To Mock
@stuherbert
• How do you prove your mock behaves accurately today?
• How do you prove your mock still behaves accurately tomorrow?
When To Mock
@stuherbert
• A mock can only be as good as the author’s understanding of whatever is being mocked
• Tests using rotted mocks will continue to pass, but the code will fail when shipped
When To Mock
@stuherbert
The Best ApproachMocks Are Sometimes
When To Mock
@stuherbert
Why?
When To Mock
@stuherbert
Is ReachableNot Every Code Path
When To Mock
@stuherbert
Testing For Failure
• How do you get bad responses from the code you call?
• How do you trigger your error handling?
When To Mock
@stuherbert
To Test For FailureMocks Are A Great Way
When To Mock
@stuherbert
In Summary
When To Mock
@stuherbert
Test what we can,
mock what we have to
When To Mock
@stuherbert
Unit TestsShould Execute Straight Out Of The Box
When To Mock
@stuherbert
Unit TestsShould Execute Straight Out Of The Box
When To Mock
✗
@stuherbert
Unit TestsShould Execute Straight Out Of The Box
As Long As Test Accuracy Is Not Compromised
When To Mock
✓
@stuherbert
Unit TestsShould Be One Of Several Layers
In Your Test Strategy
When To Mock
@stuherbert
Use Other LayersTo Test For Things You Can’t Prove
Because Of Your Mocks
When To Mock
@stuherbert
• Storyplayer for factory acceptance testing
• Behat / BDD for product acceptance testing
When To Mock
@stuherbert
Thank YouAny Questions?
When To Mock
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