when to mock · when to mock @stuherbert $ git clone [email protected]:foo/bar.git $ cd bar $ composer...

@stuherbert

When To Mock

@stuherbert

Introductions

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of Unit TestingThe Holy Grail

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@stuherbertWhen To Mock

$ git clone [email protected]:foo/bar.git $ cd bar $ composer install $ phpunit

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Unit TestsShould Execute Straight Out Of The Box

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This Was EasyIn The Pre-Web World

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• Our code wasn’t networked

• Our code used embedded data storage engines

• Our code wasn’t multi-user

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Self-ContainedOur Code Was

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Pre-Web Architecture Diagram

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Pre-Web Architecture Diagram

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Application Stack

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Talks To ThingsToday’s Code

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Self ContainedToday’s Code Is Anything But

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Our Code Has Evolved From This

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Application Stack

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Our Code Now Looks Like This

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Database

Cache1

2

3

Internal Services

External Services

Controller Models

Views

Framework

LibrariesLibrariesLibraries

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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


@stuherbert

Storage Is Now A Service

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Database

Cache1

2

3

Internal Services

External Services

Controller Models

Views

Framework


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Functionality Is Now A Service

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Database

Cache1

2

3

Internal Services

External Services

Controller Models

Views

Framework


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Apps Are Now A Service To Users

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Database

Cache1

2

3

Internal Services

External Services

Controller Models

Views

Framework


@stuherbert


When To Mock

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Good Advice?Is This Still

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Still Good Advice?

• Makes testing reproducible

• Ease of use by new project members

• Supports continuous integration

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When To Mock

✓

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Now Requires HelpMaking Unit Tests Execute Out Of The Box

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We Want To Unit Test Like This

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Application Stack

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Are GoneBut Those Days

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Our App Now Needs These

When To Mock

Database

Cache

Internal Services

External Services

@stuherbert

If We Mock These

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Database

Cache

Internal Services

External Services

@stuherbert

We Can Unit Test Without Them

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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

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• Can we mock all the things?

• Should we mock all the things?

• Should we mock inside our app?

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All The Things?Can We Mock

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• Given enough time and effort, yes we can

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All The Things?Should We Mock

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• 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?

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@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

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Test what we can,

mock what we have to

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Inside Our App?Should We Mock

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Our Code?What Happens Inside

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• computation

• branching

• input / output

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Forming Execution Paths

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One Execution PathEach Unit Test Exercises

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Such As This

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Or This

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The Code You Call?What Happens When You Mock

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Adding MocksShortens The Paths We Can Test

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Take A Code Path

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Inject A Mock

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Shorter Code Path

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Behind The Mock?But What About The Code

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?

Unreachable Code

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?

?

?

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Unreachable CodeMocks Inside Your App Create

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Is Untestable CodeUnreachable Code

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What Is The RiskFrom The Code That You Can’t Test?

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Key Questions



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@stuherbert



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

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Why?

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Is ReachableNot Every Code Path

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Testing For Failure

• How do you get bad responses from the code you call?

• How do you trigger your error handling?

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To Test For FailureMocks Are A Great Way

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In Summary

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Test what we can,

mock what we have to

When To Mock

@stuherbert


When To Mock

@stuherbert


When To Mock

✗

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As Long As Test Accuracy Is Not Compromised

When To Mock

✓

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Unit TestsShould Be One Of Several Layers

In Your Test Strategy

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Use Other LayersTo Test For Things You Can’t Prove

Because Of Your Mocks

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• Storyplayer for factory acceptance testing

• Behat / BDD for product acceptance testing

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Thank YouAny Questions?

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when to mock · when to mock @stuherbert $ git clone [email protected]:foo/bar.git $ cd bar $ composer...

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