confidence.js - Speaker Deck

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conﬁdence.js

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"I don't test-drive my JavaScript because it changes too often" - Anonymous

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Why does it change more often?

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Because it has more reasons to!

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$(function(){ });

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$(function(){ var $button = $('.submit-button'); });

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$(function(){ var $button = $('.submit-button'); $button.live('click', function(){ }); });

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$(function(){ var $button = $('.submit-button'); $button.live('click', function(){ var $input = $('input.secret-code'); }); });

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$(function(){ var $button = $('.submit-button'); $button.live('click', function(){ var $input = $('input.secret-code'); $.ajax({ }); }); });

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$(function(){ var $button = $('.submit-button'); $button.live('click', function(){ var $input = $('input.secret-code'); $.ajax({ data: $input.val() }); }); });

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$(function(){ var $button = $('.submit-button'); $button.live('click', function(){ var $input = $('input.secret-code'); $.ajax({ data: $input.val(), success: function(data){ } }); }); });

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$(function(){ var $button = $('.submit-button'); $button.live('click', function(){ var $input = $('input.secret-code'); $.ajax({ data: $input.val(), success: function(data){ $('.messages').append( '

Success! '+data.result+'

' ); } }); }); });

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$(function(){ var $button = $('.submit-button'); $button.live('click', function(){ var $input = $('input.secret-code'); $.ajax({ data: $input.val(), success: function(data){ $('.messages').append( '

Success! '+data.result+'

' ); } }); }); });

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simple!

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$(function(){ var $button = $('.submit-button'); $button.live('click', function(){ var $input = $('input.secret-code'); $.ajax({ data: $input.val(), success: function(data){ $('.messages').append( '

Success! '+data.result+'

' ); } }); }); });

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$(function(){ var $button = $('.submit-button'); $button.live('click', function(){ var $input = $('input.secret-code'); $.ajax({ data: $input.val(), success: function(data){ $('.messages').append( '

Success! '+data.result+'

' ); } }); }); }); anonymous, not reusable

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$(function(){ var $button = $('.submit-button'); $button.live('click', function(){ var $input = $('input.secret-code'); $.ajax({ data: $input.val(), success: function(data){ $('.messages').append( '

Success! '+data.result+'

' ); } }); }); }); anonymous, not reusable handle page event

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$(function(){ var $button = $('.submit-button'); $button.live('click', function(){ var $input = $('input.secret-code'); $.ajax({ data: $input.val(), success: function(data){ $('.messages').append( '

Success! '+data.result+'

' ); } }); }); }); anonymous, not reusable handle page event user event handling

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$(function(){ var $button = $('.submit-button'); $button.live('click', function(){ var $input = $('input.secret-code'); $.ajax({ data: $input.val(), success: function(data){ $('.messages').append( '

Success! '+data.result+'

' ); } }); }); }); anonymous, not reusable handle page event user event handling sends a network request

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$(function(){ var $button = $('.submit-button'); $button.live('click', function(){ var $input = $('input.secret-code'); $.ajax({ data: $input.val(), success: function(data){ $('.messages').append( '

Success! '+data.result+'

' ); } }); }); }); anonymous, not reusable handle page event user event handling sends a network request form processing

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$(function(){ var $button = $('.submit-button'); $button.live('click', function(){ var $input = $('input.secret-code'); $.ajax({ data: $input.val(), success: function(data){ $('.messages').append( '

Success! '+data.result+'

' ); } }); }); }); anonymous, not reusable handle page event user event handling sends a network request form processing network event handling

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$(function(){ var $button = $('.submit-button'); $button.live('click', function(){ var $input = $('input.secret-code'); $.ajax({ data: $input.val(), success: function(data){ $('.messages').append( '

Success! '+data.result+'

' ); } }); }); }); anonymous, not reusable handle page event user event handling sends a network request form processing network event handling HTML templating

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$(function(){ var $button = $('.submit-button'); $button.live('click', function(){ var $input = $('input.secret-code'); $.ajax({ data: $input.val(), success: function(data){ $('.messages').append( '

Success! '+data.result+'

' ); } }); }); }); anonymous, not reusable handle page event user event handling sends a network request form processing network event handling HTML templating

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SRP, or...

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SR—WHEE!

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information density

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can we test that code as-is?

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No content

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describe("~ clicking a button ", function() { var $button, $input, $messages; beforeEach(function(){ $button = affix('.submit-button'); $input = affix('input.secret-code').val('ZOMG!'); $messages = affix('.messages'); spyOn($, "ajax"); $button.trigger('click'); }); it("transmits secret code", function() { expect($.ajax).toHaveBeenCalledWith({ data: 'ZOMG!', success: jasmine.any(Function) }); }); describe("~ AJAX success", function() { beforeEach(function() { $.ajax.mostRecentCall.args[0].success({ result: "Panda!" }); }); it("appends text", function() { expect($messages).toHaveHtml( '

Success! Panda!

'); }); }); });

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describe("~ clicking a button ", function() { beforeEach(function(){ ... $button.trigger('click'); }); it("transmits secret code", function() { expect($.ajax).toHaveBeenCalledWith({ data: 'ZOMG!', success: jasmine.any(Function) }); }); ...

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describe("~ clicking a button ", function() { beforeEach(function(){ ... $button.trigger('click'); }); ... describe("~ AJAX success", function() { beforeEach(function() { $.ajax.mostRecentCall.args[0].success({ result: "Panda!" }); }); it("appends text", function() { expect($messages).toHaveHtml( '

Success! Panda!

'); }); }); });

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No content

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Testing vs. TDD

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let's talk feedback

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What can a full-stack test tell us?

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1. A feature is implemented

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2. The application seems to be working

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3. We didn't just break everything

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What can a unit test tell us?

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1. How the unit behaves

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2. How the unit depends on other units

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3. How great/awful the unit's API is

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TDD isn't about catching bugs

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TDD isn't about preventing bugs

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TDD isn't about testing

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TDD is about thinking harder

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...we can't look at testing mechanistically. Unit testing does not improve quality just by catching errors at the unit level... The truth is more subtle than that. Quality is a function of thought and reﬂection - precise thought and reﬂection. That’s the magic. Techniques which reinforce that discipline invariably increase quality. -Michael Feathers " "

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TDD is about responding to painful designs

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TDD is about discovering what we need

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TDD is not the only way

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let's try again

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our serious app has invoices

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describe("app.models.Invoice", function() { });

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describe("app.models.Invoice", function() { var subject; });

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describe("app.models.Invoice", function() { var subject; beforeEach(function() { }); });

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describe("app.models.Invoice", function() { var subject; beforeEach(function() { subject = app.models.Invoice(); }); });

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describe("app.models.Invoice", function() { var subject; beforeEach(function() { subject = app.models.Invoice({ price: 192, quantity: 30}); }); });

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describe("app.models.Invoice", function() { var subject; beforeEach(function() { subject = app.models.Invoice({ price: 192, quantity: 30}); }); describe("#total", function() { }); });

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describe("app.models.Invoice", function() { var subject; beforeEach(function() { subject = app.models.Invoice({ price: 192, quantity: 30}); }); describe("#total", function() { it("is price x quantity", function() { }); }); });

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app.models.Invoice = function(attrs) { return { total: function() { return attrs.price * attrs.quantity; } }; };

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Now, in Co eeVision

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describe "app.models.Invoice", -> beforeEach -> @subject = app.models.Invoice price: 192 quantity: 30 describe "#total", -> it "is price x quantity", -> expect(@subject.total()).toEqual(5760)

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now, in Given-When-Then w/ jasmine-given

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describe "app.models.Invoice", -> Given -> @subject = app.models.Invoice price: 192 quantity: 30 describe "#total", -> Then -> @subject.total() == 192 * 30

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describe "app.models.Invoice", -> beforeEach -> @subject = app.models.Invoice price: 192 quantity: 30 describe "#total", -> it "is price x quantity", -> expect(@subject.total()).toEqual(5760)

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let's inﬂict some pain

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formatting dollars

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app.models.Invoice = (attrs) -> self = {} self.total = -> attrs.price * attrs.quantity self

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app.models.Invoice = (attrs) -> self = {} self.total = -> attrs.price * attrs.quantity self.formattedTotal = -> "$#{self.total() / 100.0}" self

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$57.6

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hrm.

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(punting on) formatting dollars

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Defer, Defer, Defer!

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describe "app.models.Invoice", -> Given -> @subject = app.models.Invoice price: 192 quantity: 30 describe "#total", -> Then -> @subject.total() == 192 * 30 describe "#formattedTotal", -> Given -> spyOn(app.format, "DollarizesCents").andReturn dollarize: -> "$57.60" When -> @result = @subject.formattedTotal() Then -> @result == "$57.60"

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spyOn(app.format, "DollarizesCents").andReturn dollarize: -> "$57.60" #1. Store the real app.format.DollarizesCents #2. Set app.format.DollarizesCents to a fake function (called a spy). #3. Tell that spy function to return some object with a dollarize method that returns the test data "$57.60" #4. After the spec runs, replace the original app.format.DollarizesCents function

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spyOn(obj, "methodName")

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jasmine.createSpy("blah")

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app.models.Invoice = (attrs) -> self = {} self.total = -> attrs.price * attrs.quantity self.formattedTotal = -> "$#{self.total() / 100.0}" self

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app.models.Invoice = (attrs) -> self = {} self.total = -> attrs.price * attrs.quantity self.formattedTotal = -> app.format.DollarizesCents(). dollarize(self.total()) self

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fake it 'til you make it

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No content

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app.models.Invoice = (attrs) -> self = {} self.total = -> attrs.price * attrs.quantity self.formattedTotal = -> app.format.DollarizesCents(). dollarize(9182128912891) self

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describe "app.models.Invoice", -> Given -> @subject = app.models.Invoice price: 192 quantity: 30 describe "#total", -> Then -> @subject.total() == 192 * 30 describe "#formattedTotal", -> Given -> spyOn(app.format, "DollarizesCents").andReturn dollarize: jasmine.createSpy().when(5760).thenReturn("$57.60") When -> @result = @subject.formattedTotal() Then -> @result == "$57.60"

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app.models.Invoice = (attrs) -> self = {} self.total = -> attrs.price * attrs.quantity self.formattedTotal = -> app.format.DollarizesCents(). dollarize(9182128912891) self

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app.models.Invoice = (attrs) -> self = {} self.total = -> attrs.price * attrs.quantity self.formattedTotal = -> app.format.DollarizesCents(). dollarize(self.total()) self

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when().thenReturn() & other spy gadgets are in jasmine-stealth

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(actually) formatting dollars

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describe "app.format.DollarizesCents", -> Given -> @subject = app.format.DollarizesCents() describe "#dollarize", -> context "0 cents", -> Then -> @subject.dollarize(0) == "$0.00"

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app.format.DollarizesCents = -> dollarize: (cents) -> "$0.00"

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Crap.

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app.format.DollarizesCents = -> dollarize: (cents) -> dollars = cents / 100.0 decimal = if dollars % 1 == 0 then "." else "" trailingZero = if cents % 10 == 0 then "0" else "" trailingDoubleZero = if cents % 100 == 0 then "0" else "" "$#{dollars}#{decimal}#{trailingZero}#{trailingDoubleZero}"

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Yuck!

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app.format.DollarizesCents = -> dollarize: (cents) -> s = "$" s += (dollars = cents / 100.0) s += "." if dollars % 1 == 0 s += "0" if cents % 10 == 0 s += "0" if cents % 100 == 0 s

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Meh.

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Let's lean into it.

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describe "app.format.DollarizesCents", -> Given -> @subject = app.format.DollarizesCents() describe "#dollarize", -> context "0 cents", -> Then -> @subject.dollarize(0) == "$0.00" context "50 cents", -> Then -> @subject.dollarize(50) == "$0.50" context "1,841,482 cents", -> Then -> @subject.dollarize(1841482) == "$18,414.82"

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app.format.DollarizesCents = -> dollarize: (cents) -> amount = cents / 100.0 s = "$" s += @commasFor(amount) s += "0" if cents % 10 == 0 s += "0" if cents % 100 == 0 s #private commasFor: (amount) -> [dollars, cents] = amount.toString().split(".") s = "" while dollars.length > 3 s = ",#{dollars.slice(-3)}#{s}" dollars = dollars.substring(0, dollars.length - 3) "#{dollars}#{s}.#{cents or ""}"

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I am now embarrassed.

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commasFor is doing too much

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app.format.DollarizesCents = -> dollarize: (pennies) -> amount = pennies / 100.0 [dollars, cents] = amount.toString().split(".") s = "$" s += @commasFor(dollars) s += ".#{cents or ""}" s += "0" if pennies % 10 == 0 s += "0" if pennies % 100 == 0 s #private commasFor: (dollars) -> s = "" while dollars.length > 3 s = ",#{dollars.slice(-3)}#{s}" dollars = dollars.substring(0, dollars.length - 3) "#{dollars}#{s}

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app.format.DollarizesCents = -> dollarize: (pennies) -> amount = pennies / 100.0 [dollars, cents] = amount.toString().split(".") s = "$" s += @commasFor(dollars) s += "." s += @paddingFor(cents) s #private commasFor: (dollars) -> s = "" while dollars.length > 3 s = ",#{dollars.slice(-3)}#{s}" dollars = dollars.substring(0, dollars.length - 3) "#{dollars}#{s}" paddingFor: (cents = "") -> while cents.length < 2 cents += "0" cents

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app.format.DollarizesCents = -> dollarize: (pennies) -> amount = pennies / 100.0 [dollars, cents] = amount.toString().split(".") "$#{@commasFor(dollars)}.#{@paddingFor(cents)}" #private commasFor: (dollars) -> s = "" while dollars.length > 3 s = ",#{dollars.slice(-3)}#{s}" dollars = dollars.substring(0, dollars.length - 3) "#{dollars}#{s}" paddingFor: (cents = "") -> while cents.length < 2 cents += "0" cents

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app.format.DollarizesCents = -> dollarize: (pennies) -> amount = (pennies / 100.0).toFixed(2) [dollars, cents] = amount.toString().split(".") "$#{@commasFor(dollars)}.#{cents}" #private commasFor: (dollars) -> s = "" while dollars.length > 3 s = ",#{dollars.slice(-3)}#{s}" dollars = dollars.substring(0, dollars.length - 3) "#{dollars}#{s}"

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what about the DOM?

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I want my asp/jsp/erb!

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No you don't.

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I want to load HTML ﬁxture ﬁles!

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No you don't.

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describe "app.views.Invoice", -> Given -> @subject = app.views.Invoice()

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describe "app.views.Invoice", -> Given -> @subject = app.views.Invoice() describe "#render", ->

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describe "app.views.Invoice", -> Given -> @subject = app.views.Invoice() describe "#render", -> Given -> @$el = $('

'). appendTo('body')

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describe "app.views.Invoice", -> Given -> @subject = app.views.Invoice() describe "#render", -> Given -> @$el = $('

'). appendTo('body') When -> @subject.render(@$el)

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describe "app.views.Invoice", -> Given -> @subject = app.views.Invoice() describe "#render", -> Given -> @$el = $('

'). appendTo('body') When -> @subject.render(@$el) Then -> expect(@$el).toContain('.total')

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app.views.Invoice = () -> render: ($el) -> $el.append("

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test pollution

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describe "app.views.Invoice", -> Given -> @model = app.models.Invoice() Given -> @subject = app.views.Invoice model: @model describe "#render", -> Given -> @$el = $('

'). appendTo('body') When -> @subject.render(@$el) Then -> expect(@$el).toContain('.total')

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describe "app.views.Invoice", -> Given -> @model = app.models.Invoice() Given -> @subject = app.views.Invoice model: @model describe "#render", -> Given -> @$el = $('

'). appendTo('body') afterEach -> @$el.remove() When -> @subject.render(@$el) Then -> expect(@$el).toContain('.total')

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describe "app.views.Invoice", -> Given -> @model = app.models.Invoice() Given -> @subject = app.views.Invoice model: @model describe "#render", -> Given -> @$el = affix('div') When -> @subject.render(@$el) Then -> expect(@$el).toContain('.total')

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jasmine-ﬁxture a x()

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it's jQuery in reverse!

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No content

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$button = affix('.button')

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$button = affix('.button') #=>

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$button = affix('.button') #=>

$button.affix('input#firstName[value="Joe"]')

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$button = affix('.button') #=>

$button.affix('input#firstName[value="Joe"]') #=>

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$button = affix('.button') #=>

$button.affix('input#firstName[value="Joe"]') #=>

affix('pre code div.example')

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$button = affix('.button') #=>

$button.affix('input#firstName[value="Joe"]') #=>

affix('pre code div.example') #=>

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$button = affix('.button') #=>

$button.affix('input#firstName[value="Joe"]') #=>

affix('pre code div.example') #=>

# And it deletes affixed elements afterEach spec!

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Now, formatted price

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describe "app.views.Invoice", -> Given -> @subject = app.views.Invoice() describe "#render", -> Given -> @$el = affix('div') When -> @subject.render(@$el) Then -> expect(@$el).toContain('.total')

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describe "app.views.Invoice", -> Given -> @model = app.models.Invoice price: 38 quantity: 2 Given -> @subject = app.views.Invoice model: @model describe "#render", -> Given -> @$el = affix('div') When -> @subject.render(@$el) Then -> expect(@$el.find('.total')). toHaveText("$0.76")

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app.views.Invoice = (config) -> render: ($el) -> $el.append "

"+ config.model.formattedTotal()+ "

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spec leakage

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the view spec knows how the model's formattedTotal works

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that's not very DRY

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collaboration > implementation

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describe "app.views.Invoice", -> Given -> @model = {} Given -> @subject = app.views.Invoice model: @model describe "#render", -> Given -> @$el = affix('div') When -> @subject.render(@$el) Then -> expect(@$el).toContain('.total') Then -> expect(@$el.find('.total')). toHaveText("$0.76")

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describe "app.views.Invoice", -> Given -> @model = {} Given -> @subject = app.views.Invoice model: @model describe "#render", -> Given -> @model.formattedTotal = jasmine.createSpy().andReturn("$foo") Given -> @$el = affix('div') When -> @subject.render(@$el) Then -> expect(@$el).toContain('.total') Then -> expect(@$el.find('.total')). toHaveText("$foo")

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TIL

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If you're not open to changing your code's design, TDD won't help.

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TDD helps us to: - think hard - respond to pain - keep moving forward (tests are a side e ect)

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When a solution isn't obvious, defer to a new object and fake it 'til you make it.