Slides of third event in TDD mini serie of the Haarlem Software Developer Meetup presented by @McBeelen

1. Test Driven Development
Driving Development by Tests
Haarlem Software Developer Meetup
@mcbeelen

2. Confidential Page 2
KvK 53479335
Lichtfabriekplein 1, 2031 TE Haarlem
P.O. Box 2031 , 2002 CA Haarlem
+31 (0)88 248 1632,
info@ximedes.com
www.ximedes.com
Meetup
Sponsor:

3. 01-10-2015Confidential Page 3

4. 01-10-2015Confidential Page 4
User Story
In order to ….. achieve some goal
As a .... actor
I want to ...... have certain functionality
Scenario: Example
Given….. some situation
When.... perform action
Then...... verify correct behaviour

5. 01-10-2015Confidential Page 5

6. 01-10-2015Confidential Page 6
Once upon a time
…

7. 01-10-2015Confidential Page 7
Controller
Validator Service
Collaborator
Converter
Acceptance
Test

8. 01-10-2015Confidential Page 8
Controller
Validator Service
Collaborator
Converter
Acceptance
Test
Unit
Test

9. 01-10-2015Confidential Page 9
Controller
Mock
Validator
Mock
Service
Obsolete
Collaborator
Mock
Converter
Unit
Test
London School of TDD

10. 01-10-2015Confidential Page 10

11. 01-10-2015Confidential Page 11
Three options to make a test pass:
1 2
Obvious Implementation

12. 01-10-2015Confidential Page 12
assertThat(calculate.multiply(2 * 5), is(10));
1 2
multiply(x, y) {
return x * y;
}
multiply(x, y) {
return 10;
}
multiply(x, y) {
return 2 * 5;
}
multiply(x, y) {
return x * y;
}

13. 01-10-2015Confidential Page 13

14. 01-10-2015Confidential Page 14
Triangulation
3

15. 01-10-2015Confidential Page 15
assertThat(calculate.multiply(2 * 5), is(10));3
multiply(x, y) {
return 10;
}
assertThat(calculate.multiply(2 * 7), is(14));
multiply(x, y) {
return 2 * y;
}
assertThat(calculate.multiply(3 * 7), is(21));
multiply(x, y) {
return x * y;
}

16. 01-10-2015Confidential Page 16
Baby steps TDD
http://www.tddfellow.com/blog/2016/10/19/do-more-with-baby-steps-tdd/

17. 01-10-2015Confidential Page 17
The Transformation Priority Premise
“As the tests get more specific,
the code gets more generic.”
https://8thlight.com/blog/uncle-bob/2013/05/27/TheTransformationPriorityPremise.html

18. 01-10-2015Confidential Page 18

19. 01-10-2015Confidential Page 19
1. You are here to LEARN.
(and have fun)
2. Try to do your best.
3. Work in pairs.
Find a partner in a similar
programming language
and operating system

20. 01-10-2015Confidential Page 20

21. 01-10-2015Confidential Page 21
1 2
Primefactors:
Factorize a positive integer
number into its prime factors.
Pokerhands:
Determine the winner given
two pokerhands.

22. See you next time: March16th
Test Driven Development
Refactoring
Haarlem Software Developer Meetup