You are previewing Testable JavaScript.

Testable JavaScript

Cover of Testable JavaScript by Mark Ethan Trostler Published by O'Reilly Media, Inc.
  1. Testable JavaScript
  2. Dedication
  3. Preface
    1. The Goal of This Book
    2. Who This Book Is For
    3. Who This Book Is Not For
    4. Who I Am
    5. What You Will Learn from This Book
      1. Content
    6. If You Like (or Don’t Like) This Book
    7. Recap
    8. How to Contact Us
    9. Conventions Used in This Book
    10. Using Code Examples
    11. Safari® Books Online
    12. Thanks!
  4. 1. Testable JavaScript
    1. Prior Art
      1. Agile Development
      2. Test-Driven Development
      3. Behavior-Driven Development
      4. The Best Approach?
    2. Code Is for People
      1. Why
      2. What
      3. How
    3. Beyond Application Code
      1. Testing
      2. Debugging
    4. Recap
  5. 2. Complexity
    1. Code Size
    2. JSLint
    3. Cyclomatic Complexity
    4. Reuse
    5. Fan-Out
    6. Fan-In
    7. Coupling
      1. Content Coupling
      2. Common Coupling
      3. Control Coupling
      4. Stamp Coupling
      5. Data Coupling
      6. No Coupling
      7. Instantiation
    8. Coupling Metrics
    9. Coupling in the Real World
      1. Testing Coupled Code
    10. Dependency Injection
    11. Comments
      1. YUIDoc
      2. JSDoc
      3. Docco/Rocco
    12. The Human Test
    13. Recap
  6. 3. Event-Based Architectures
    1. The Benefits of Event-Based Programming
    2. The Event Hub
      1. Using the Event Hub
      2. Responses to Thrown Events
      3. Event-Based Architectures and MVC Approaches
      4. Event-Based Architectures and Object-Oriented Programming
      5. Event-Based Architectures and Software as a Service
    3. Web-Based Applications
    4. Testing Event-Based Architectures
    5. Caveats to Event-Based Architectures
      1. Scalability
      2. Broadcasting
      3. Runtime Checking
      4. Security
      5. State
    6. A Smarter Hub: The Event Switch
      1. Deployment
      2. An Implementation
      3. Sessions
      4. Extensibility
    7. Recap
  7. 4. Unit Tests
    1. A Framework
    2. Let’s Get Clean
    3. Writing Good Tests
      1. Isolation
      2. Scope
      3. Defining Your Functions
      4. Positive Testing
      5. Negative Testing
      6. Code Coverage
    4. Real-World Testing
      1. Dependencies
      2. Asynchronous Testing
    5. Running Tests: Client-Side JavaScript
      1. PhantomJS
      2. Selenium
    6. Running Tests: Server-Side JavaScript
      1. Jasmine
    7. Recap
  8. 5. Code Coverage
    1. Coverage Basics
    2. Code Coverage Data
    3. A Hands-on Example
      1. Instrumenting Files
      2. Anatomy of a Coveraged File
    4. Exercise/Deploy
      1. Client-Side JavaScript
      2. Server-Side JavaScript
    5. Persisting Coverage Information
      1. Unit Tests
      2. Integration Tests
    6. Generating Output
    7. Aggregation
    8. Hidden Files
    9. Coverage Goals
    10. Recap
  9. 6. Integration, Performance, and Load Testing
    1. Integration Testing
      1. Selenium
      2. CasperJS
    2. Performance Testing
      1. Generating HAR Files
      2. Viewing HAR Files
      3. Browser Performance Testing
    3. Load Testing
      1. Browser Load Testing
    4. Tracking Resource Usage
      1. Client-Side Tracking
      2. Server-Side Tracking
    5. Recap
  10. 7. Debugging
    1. In-Browser Debugging
      1. Firefox
      2. Chrome
      3. Safari
      4. Internet Explorer
    2. Node.js Debugging
    3. Remote Debugging
      1. Chrome
      2. PhantomJS
      3. Firefox
    4. Mobile Debugging
      1. Android 4
      2. iOS 6
      3. Adobe Edge Inspect
      4. Other Mobile Debugging Options
    5. Production Debugging
      1. Minified Code
      2. Source Maps
    6. Recap
  11. 8. Automation
    1. What to Automate
    2. When to Automate
    3. How to Automate
      1. Automating with Continuous Integration
      2. Automating the Development Environment
      3. Automating the Build Environment
      4. Deployment
    4. Recap
  12. Index
  13. About the Author
  14. Colophon
  15. Copyright
O'Reilly logo

Chapter 3. Event-Based Architectures

Using factories of various abstractions, façades, and other patterns is not the only way to decouple dependencies and isolate code. A more JavaScript-oriented approach involves the use of events. The functional nature of JavaScript makes it an ideal language for event-based programming.

The Benefits of Event-Based Programming

At their core, all applications revolve around message passing. Tight coupling can occur because the code needs to have a reference to another object so that it can send the object a message and perhaps receive a reply. These objects are global, passed in, or injected via a function parameter, or they are instantiated locally. Our use of factories in the preceding chapter enabled us to pry away the local instantiation requirement; however, we still need the object to be available locally in order to pass messages to it, which means we still must deal with global or injected dependencies. Global dependencies are dangerous: any part of the system can touch them, making bugs very difficult to track down; we can accidentally change them if we have a variable by the same or a similar name declared locally; and they cause data encapsulation to break since they are available everywhere, making debugging very difficult. JavaScript makes declaration and use of global variables very easy, and the environment typically provides several global variables (e.g., the window object in the global scope), as well as global functions and objects ...

The best content for your career. Discover unlimited learning on demand for around $1/day.