This document discusses test-driven development (TDD) with Node.js. TDD involves writing failing tests before code, making tests pass by writing the minimum code, and then refactoring. Using TDD can lead to less fear of change, increased productivity, better communication, improved design, and fewer bugs. Tests should start at the public interface and mock dependencies. Tests should keep it simple and focus on the interface being tested. Tools like proxyquire and Sinon can help with dependency injection and spies/stubs, while Istanbul can measure code coverage, though coverage alone does not mean code is tested. Overall, TDD concepts are more important than specific tools.

1. Test-driven development
with Node.js
@mirkokiefer
Mirko Kiefer - mail@mirkokiefer.com

2. What is TDD?

3. Why use TDD?
• Less fear of change
• Increase productivity and focus
• Better communication in teams
• Improved software design
• Less bugs

4. Test in layers
• Start with the public interface (API / user interface)
• Mock the next (non-implemented) layer underneath
• Repeat with implementing the next layer
• Example:
user interface -> server API -> request handlers -> database

5. Write failing test
• Imagine the interface you wish
• Does not have to compile
• Keep it simple

6. Make test pass
• Quickest solution possible
• Sins are allowed
• Fake it till you make it

7. Refactor
• Remove duplication
• If obvious, write “correct” implementation
• Write next failing test

8. Fake it till you make it!

9. How to fake it?

10. Dependency Injection

11. Enter proxyquire()
• Dependency injection without changing your code
• Does not fiddle with globals

12. Spies and stubs
self-made

13. Spies and stubs
Sinon.JS

14. Code coverage
Istanbul

15. Code coverage
• Don’t be fanatic
• Code covered does not mean its tested
• You know which code is critical

16. Keep it simple
• Do you really need tools for mocking and
dependency injection?
• Tools introduce complexity and can slow you down
• Embrace concepts, not tools

17. Mirko Kiefer
@mirkokiefer
mail@mirkokiefer.com
Questions?