When To Mock

@stuherbert When To Mock

@stuherbert Introductions When To Mock

@stuherbert of Unit Testing The Holy Grail When To Mock

@stuherbert When To Mock $ git clone git@github.com:foo/bar.git $ cd
bar $ composer install $ phpunit

@stuherbert Unit Tests Should Execute Straight Out Of The Box
When To Mock

@stuherbert This Was Easy In 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 Self-Contained Our Code Was When To Mock

@stuherbert Pre-Web Architecture Diagram When To Mock

@stuherbert Pre-Web Architecture Diagram When To Mock Application Stack

@stuherbert Talks To Things Today’s Code When To Mock

@stuherbert Self Contained Today’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 Cache 1 2 3 Internal Services External Services Controller Models Views Framework Libraries Libraries Libraries

@stuherbert Internally, More Complexity When To Mock Database Cache 1
2 3 Internal Services External Services Controller Models Views Framework Libraries

@stuherbert Internally, More Dependencies When To Mock Database Cache 1
2 3 Internal Services External Services Controller Models Views Framework Libraries Libraries Libraries

@stuherbert Storage Is Now A Service When To Mock Database
Cache 1 2 3 Internal Services External Services Controller Models Views Framework Libraries Libraries Libraries

@stuherbert Functionality Is Now A Service When To Mock Database
Cache 1 2 3 Internal Services External Services Controller Models Views Framework Libraries Libraries Libraries

@stuherbert Apps Are Now A Service To Users When To
Mock Database Cache 1 2 3 Internal Services External Services Controller Models Views Framework Libraries Libraries Libraries

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

When To Mock ✓

@stuherbert Now Requires Help Making 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 Gone But 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 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 • 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 Forming Execution Paths When To Mock

@stuherbert One Execution Path Each Unit Test Exercises When To
Mock

@stuherbert Such As 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 Mocks Shortens 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 Code Mocks Inside Your App Create When To
Mock

@stuherbert Is Untestable Code Unreachable Code When To Mock

@stuherbert What Is The Risk From 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 Approach Mocks Are Sometimes When To Mock

@stuherbert Why? When To Mock

@stuherbert Is Reachable Not 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 Failure Mocks 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

When To Mock

When To Mock ✗

As Long As Test Accuracy Is Not Compromised When To Mock ✓

@stuherbert Unit Tests Should Be One Of Several Layers In
Your Test Strategy When To Mock

@stuherbert Use Other Layers To 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 You Any Questions? When To Mock

When To Mock

When To Mock

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