1. Practiced Agile
Developer with TDD and
BDD
by Sakares Saengkaew
Software Development and Quality Improvement,
Asian Institute of Technology

2. How many hours testing of your
software? When will you perform
testing? What happens?
● 8 hours?
● 10 % of project work hours.
● before deployment 5 days and some bugs
still be unsolved left.
● complicate unsolvable bug.
● Need more time to debug.
● Just show to customer and wish they will not
see unexpected scene.

3. How should we make it
better?
- Change the way of coding
by TDD !

4. What's TDD ?
- abbreviated from "Test Driven Development".
- a programming technique based on a very
simple rule :
Only ever write code to fix a failing test.

5. What's TDD ?
- Test first, then code and design afterward.

6. What's TDD ?
- But It's not finished yet.
- We call it refactoring to better communicate
that the last step is about transforming the
current design toward a better design.

7. How to ?
- Using Unit Test. For example, JUnit in Java,
BoostTest in C++ or UnitTest in Ruby on Rails.
- Perform Red-Green-Refactor principle.

8. Red-Green-Refactor
- Firstly, write a test. Hence, it failed (Red)
since there is no functionality code at start.
- Secondly, make it pass by simply
implementing the missing functionality. Then it
turn pass (Green).
- Last, refactoring. As we improve the design of
the code without altering its external behavior,
all tests should pass and, thus, we should
remain green.

9. Brief summary : TDD
- TDD is when you use Automated Testing
(usually Unit Testing) as a design practice.
- TDD ensures high quality code.
- Release work with confident.
- Make a collective code ownership since unit
test suite is a clear document that every
developer in teams can read, follow and write
by individual.

10. But the defect of TDD
- The unit tests still test the behavior of the
method.
- It may be difficult to trace the behavior of the
method directly to the behavior that the external
stakeholders asked for and/or understand.
- Hence, we consider BDD .

11. What's BDD ?
- abbreviated from "Behavior Driven
Development".
- BDD is an extension/revision of TDD.
- BDD specifies that tests of any unit of
software should be specified in terms of the
desired behavior of the unit.

12. What's BDD ?
- Borrowing from agile software development
the "desired behavior" in this case consists of
the requirements set by the business.
- BDD utilizes a "Ubiquitous Language", a body
of knowledge that can be understood by both
the developer and the customer. Moreover, it is
used to shape and develop the requirements
and testing needed, at the level of the
customer's understanding.

13. How to ?
- Popular BDD tools include Cucumber, RSpec,
SpecFlow and others.
- To explain how to perform simply BDD, we
will illustrate from the Cucumber tool by Ruby
language .

14. BDD by Cucumber
1: Describe behaviour in plain text

15. BDD by Cucumber
2: Write a step definition in Ruby

16. BDD by Cucumber
3: Run and watch it fail

17. BDD by Cucumber
4: Write code to make the step pass

18. BDD by Cucumber
5: Run again and see the step pass

19. BDD by Cucumber
6: Repeat 2-5 until green like a cuke

20. Brief summary : BDD
- BDD is when you use Automated Testing to
flesh out & capture domain logic starting from
the (high-enough) functional testing down to the
domain unit logic.
- BDD ensures high cohesion between
technical implementation and the domain.
- makes sense to business via the domain units
and behaviour that domain experts understand.

21. Summary : What's different
between TDD and BDD ?
- BDD focuses on the behavioural aspect of the
system rather than the implementation aspect
of the system that TDD focuses on.
- BDD gives a clearer understanding as to what
the system should do from the perspective of
the developer and the customer.
- TDD only gives the developer an
understanding of what the system should do.

22. Summary
- One of the principles in agile, "Responding
to change over following a plan". This means
that do not know in advance what you have to
build.
- TDD and BDD support the change since you
can write exactly needed feature. Also prevent
overproduction.

23. Summary
- "Customer collaboration over contract
negotiation". It's clear by using BDD.
Customer become to cooperate in software
development. Sharpen the product requirement
in business aspect.

24. Reference
● Practices of an agile developer: working in the real world
by Venkat Subramaniam, Andy Hunt
● Test Driven: Practical TDD and Acceptance TDD for Java
Developers by Lasse Koskela
● The Cucumber Book: Behaviour-Driven Development for
Testers and Developers by Matt Wynne, Matt Wynne
● http://www.anitpatel.net/2012/06/14/what-is-the-difference-
between-tddatddbdd-in-agile-development/
● http://en.wikipedia.org/wiki/Behavior-driven_development
● http://programmers.stackexchange.
com/questions/21870/can-you-be-agile-without-doing-tdd-
test-driven-development
● http://cukes.info/