Mark Trostler - discusses about testability in javascript. I think the main take away is that interfaces should be exposed and the interface should do only one thing so for e.g., have set, get, delete, etc., operations. He has written a book on testability in Javascript and given other sessions at different conferences. See here. Interface Pattern:

• Single Responsibility Principle
• Match sets with gets
• more smaller/fewer bigger
• Interfaces segregation principle
• Test and Program to interface Only

  Liskov Substituion Principle Any objects that implement an interface can be used interchangeably