tea-time/presentation/08_mocks_and_stubs.slides

!SLIDE even-larger
``` coffeescript
describe
it
expect
toSomething()
beforeEach
afterEach
```

!SLIDE
# Jasmine == unit testing

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<img src="assets/synergize.jpg" />

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# No, this isn't a talk about integration testing

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# Testing the *right* things in your JavaScript unit tests

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<img src="assets/spaghetti.jpg" />

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# John behavior #2
## Mock, stub, and spy on anything that should be handled in an integration test

``` coffeescript
describe 'John', ->
  describe 'spec definitions', ->
    it 'should keep unit tests as focused as possible', ->
```

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<img src="assets/beer-cat.jpg" />

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``` gherkin
Feature: Cat Behaviors
  Scenario: Hungry cats meow a particular way
    Given I have a cat
      And the cat is hungry
    When the cat meows
    Then the meow should sound like "meeyaow"
```

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``` coffeescript
class this.Cat
  @FOOD_THRESHOLD = 20
  @HUNGRY = 'hungry'

  constructor: (@foodLevel = 30) ->

  meow: ->
    switch this.state()
      when Cat.HUNGRY
        "meeyaow"

  state: ->
    if @foodLevel < Cat.FOOD_THRESHOLD
      Cat.HUNGRY
```

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``` coffeescript
describe 'Cat', ->
  describe '#meow', ->
    context 'hungry', ->
      it 'should be a mournful meow', ->
        cat = new Cat()
        cat.foodLevel = 15

        expect(cat.meow()).toEqual("meeeyaow")
```

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# A perfectly cromulent test

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``` coffeescript
class this.Cat
  meow: ->
    switch this.state() # <= dependent code executed
      when Cat.HUNGRY
        "meeyaow"
```

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# Why make your unit tests fragile?

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``` coffeescript
cat.foodLevel = 15
  # do we care about food level in this test?
    # all we care about is that the cat is hungry
```

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``` coffeescript
describe 'Cat', ->
  describe '#meow', ->
    describe 'hungry', ->
      it 'should be a mournful meow', ->
        cat = new Cat()
        cat.state = -> Cat.HUNGRY
          # ^^^ we don't care how state works,
            # we just want a hungry cat

        expect(cat.meow()).toEqual("meeeyaow")
```

!SLIDE
# Instance Stubs in JavaScript
## Just replace the method on the instance

``` coffeescript
class this.Cat
  state: ->
    # cat codes

cat = new Cat()
cat.state = -> "whatever"
```

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# Stubs just return something when called

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# Mocks expect to be called

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# Test fails if all mocks are not called

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# Jasmine blurs the line a little

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<img src="assets/spy-cat.jpg" />

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# Spies work like mocks, but with additional abilities

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<img src="assets/flying-cat.jpg" />

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``` coffeescript
class this.Cat
  vocalProcessor: (speech) =>
    if this.isAirborne()
      this.modifyForAirborne(speech)
    else
      this.modifyForGround(speech)
```

!SLIDE
``` coffeescript
describe 'Cat#vocalProcessor', ->
  speech = "speech"

  beforeEach ->
    @cat = new Cat()

  context 'airborne', ->
    beforeEach ->
      spyOn(@cat, 'modifyForAirborne')
      @cat.isAirborne = -> true

    it 'should be modified for flight', ->
      @cat.vocalProcessor(speech)
      expect(@cat.modifyForAirborne).toHaveBeenCalledWith(speech)
```

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# `spyOn` replaces a method on an instance with a spy method

``` coffeescript
spyOn(@cat, 'modifyForAirborne')
```

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# Can return a value, run code, run the original code, or just wait to be called

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# Two basic ways to make sure a spy is called

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## `toHaveBeenCalledWith(args...)`
### Called least once with the given parameters

``` coffeescript
expect(@cat.modifyForAirborne).toHaveBeenCalledWith(speech)
```

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## `toHaveBeenCalled()`
### Just called, no parameter check

``` coffeescript
expect(@cat.modifyForAirborne).toHaveBeenCalled()
```

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# Instance Mocks/Spies in JavaScript
## Use `spyOn`/`toHaveBeenCalled` matchers

``` coffeescript
class this.Cat
  state: ->
    # cat codes

cat = new Cat()
spyOn(cat, 'state')
expect(cat.state).toHaveBeenCalled()
```

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# `spyOn` works great with class-level stubs and mocks, too

!SLIDE
``` coffeescript
class this.Cat
  @generateFurColor: (base) ->
    # magicks to make a fur color given a base

  regrowFur: (damagedHairs) ->
    for follicle in damagedHairs
      follicle.regrow(Cat.generateFurColor(this.baseColor))
```

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``` coffeescript
Cat.generateFurColor = ->
  "whoops i nuked this method for every other test"
```

!SLIDE
``` coffeescript
describe 'Cat#regrowFur', ->
  color = 'color'

  beforeEach ->
    @cat = new Cat()
    @follicle =
      regrow: ->

    @follicles = [ follicle ]

    spyOn(Cat, 'generateFurColor').andReturn(color)
    #           ^^^ original is replaced when done
    spyOn(@follicle, 'regrow')

  it 'should regrow', ->
    @cat.regrowFur(@follicles)

    expect(@follicle.regrow).toHaveBeenCalledWith(color)
```

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# Class Stubs in JavaScript
## Use `spyOn` to generate stubs so that the original code is replaced after the test

``` coffeescript
class this.Cat
  @injectPsychicPowers: (cat) ->
    # cat codes

spyOn(Cat, 'injectPsychicPowers').andReturn(psychicCat)
```

!SLIDE
# John behavior #3
## If you have too many mocks/stubs/contexts, your code is too complex

``` coffeescript
describe 'John', ->
  describe 'spec definitions', ->
    it 'should obey the Law of Demeter as much as possible', ->
    it 'should not smell too funny', ->
```

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``` coffeescript
describe 'Cat#fetch', ->
  object = null

  context 'a mouse', ->
    beforeEach ->
      object = new Mouse()

    context 'fast mouse', ->
      it 'should wear down the mouse', ->
        # who

    context 'slow mouse', ->
      it 'should deliver a present to you', ->
        # cares

  context 'a ball', ->
    beforeEach ->
      object = new Ball()

    context 'ball is bouncing', ->
      it 'should cause the cat to leap', ->
        # this

    context 'ball is rolling', ->
      it 'should cause the cat to slide on the floor', ->
        # test

  context 'a red dot', ->
    laser = null

    beforeEach ->
      laser = new Laser()

    context 'laser out of batteries', ->
      it 'should not activate', ->
        # is

    context 'laser functioning', ->
      it 'should activate, driving the cat insane', ->
        # huge and unmaintainable and silly
```

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# Sometimes you just need a big blob of unit tests

!SLIDE
``` coffeescript
# fast and focused!

describe 'Cat#respondsTo', ->
  beforeEach ->
    @cat = new Cat()

  context 'successes', ->
    it 'should respond', ->
      for request in [ 'kitty kitty', 'pookums', 'hisshead' ]
        expect(@cat.respondsTo(request)).toBeTruthy()
```

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``` gherkin
# slow and synergistic!

Scenario Outline: Successful responsiveness
  Given I have a cat
  When I call it with "<request>"
  Then the cat should respond

  Examples:
    | request     |
    | kitty kitty |
    | pookums     |
    | hisshead    |
```

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<img src="assets/balancing-cat.jpg" />

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# Find what works best for you and stick with it

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## ...until you get sick of it, of course...