Test Driven Development (TDD) follows three main laws: only write production code to pass a failing test, only write enough test code to fail, and only write enough production code to pass the test. TDD brings benefits like improved debugging, courage to refactor, documentation, and design. Good unit tests are atomic, isolated, repeatable, revealing, and fast. The structure of a test is to arrange inputs, act on the system under test, and assert the expected outcomes. Strategies for TDD include using obvious implementations, faking dependencies, and triangulating tests. Practicing TDD involves code katas, communities, and conferences.

1. Test Driven Development
Aim loosely
@pedromsantos

2. Fail to succeed

3. Red, Green, Refactor
The TDD mantra

4. Laws
• You are not allowed to write any production code
unless it is to make a failing unit test pass.
• You are not allowed to write any more of a unit
test than is sufficient to fail; and compilation
failures are failures.
• You are not allowed to write any more production
code than is sufficient to pass the one failing unit
test.

5. Benefits
• Debugging
• Courage
• Documentation
• Design
• Professionalism

6. Qualities of a Good Unit Test
• Atomic
• Isolated
• Repeatable
• Revealing
• Easy to Setup
• Fast

7. Inside a test
• Arrange – all necessary preconditions and
inputs
• Act – on the object or method under test
• Assert – that the expected results have occurred
• Assert First?

8. Strategies
• Use Obvious Implementation
• Fake it
• Triangulate

9. Practice
• Code Kata
• Community
• London Software Craftsmanship Community

10. Demo

11. SoCraTes UK 2014
International Software Craftsmanship gathering
12th – 15th June, Farncombe Estate
!
http://socratesuk.org/

12. References
• http://www.amazon.com/exec/obidos/ASIN/
0321146530/ambysoftinc

13. References
• https://leanpub.com/socra

14. References
• http://www.meetup.com/london-software-
craftsmanship/
• http://codingdojo.org/cgi-bin/index.pl?
KataCatalogue
• http://cyber-dojo.org/
• http://programmer.97things.oreilly.com/wiki/
index.php/The_Three_Laws_of_Test-
Driven_Development

15. Thank you!
@pedromsantos