JavaScript Unit Testing

1. Shabnam Shahfar
@ShabnamShahfar
Prairie Dev Con, 2014Protegra

2.  What is a unit test?
 Test Driven Development
 Running a unit test in a browser
 Libraries and Frameworks
 Writing Testable JavaScript
 Exercise/Demo
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4.  A test for the smallest testable part of your
application
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5.  Isolated and Independent
 Repeatable
 Small
 Easy to read
 Fast
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8.  Find problems early
 Develop & refactor with confidence
 Easier than testing manually
 Documentation
 On-going Regression Testing
 Better Design
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9. “Do the pieces work together as expected?”
 Simulate user’s behavior
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10.  They don’t help you write better code, they
just make sure your application still works.
 Slower than unit testing
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13.  Block Scope vs. Function Scope
 Proxy Objects
 Simulating DOM Events
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14.  Function scope also means that variables
declared inside functions are only available
inside those functions, once the function
exits, the variables are inaccessible.
 JavaScript does have private variables. You
declare them inside closures.
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15.  Block Scope vs. Function Scope
 Proxy Objects
 Simulating DOM Events
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17.  Block Scope vs. Function Scope
 Proxy Objects
 Simulating DOM Events
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18.  Example
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19.  Code organization
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Presentation &
Interaction
Application State
Data/Server
Communication
Setup

22.  Anonymous functions, lack of structure
 Complex, oversized functions
 Hidden or shared state
 Tightly coupled
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27.  Keep methods simple
 Don’t intermingle responsibilities
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28. Write test first!
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29. Books:
 JavaScript the good parts, by Douglas
Crockford
 JavaScript unit testing, by Hazem Saleh
 http://alistapart.com/article/writing-
testable-javascript
 http://www.adequatelygood.com/Writing-
Testable-JavaScript.html
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