This document provides an overview of Test Driven Development (TDD). It discusses the core principles of TDD including writing a failing test first, then only writing enough code to pass that test, and refactoring code if needed. The document outlines the TDD process with steps of writing a failing test, writing just enough code to pass the test, and refactoring code if needed. It notes benefits of TDD include code that is always backed by tests, decoupled design, and automatically having full test coverage and regression tests.

1. TDD 101
1. Test Driven Development

2. Test Driven Development

3. Test Driven
Development
It’s a discipline
Unit test first
Only code to pass the test
Loop of minimal changes

4. Classic post-test vs TDD
TestCodeDesign
DesignCodeTest
Waterfall
TDD

5. TDD laws

6. TDD laws
You can't write any
production code
until you have first
written a failing unit
test.
You can't write
more of a unit test
than is sufficient to
fail, and not
compiling is failing.
You can't write
more production
code than is
sufficient to pass
the currently failing
unit test.
Robert C. Martin

7. TDD cycle

8. TDD cycle
Write a
failing test
Write just
enough code
to make the
test pass
Refactor if
needed
(mostly
reduce
duplication)

9. Write a failing test
Write a test to
prove a simple case
Run the test and
see how it fails
Errors == test fails

10. Make the test pass
Write production
code until:
• all errors are fixed
• the test passes

11. Refactor
Keep tests passing
Remove duplication
Improve design

12. Outcomes

13. Outcomes Always backed by tests
Decoupled design
Automatically you get:
• full coverage
• regression tests

14. Code

15. Write a failing test
class ValidateNifTest extends TestCase
{
public function testRealNIFShouldBeValid()
{
$validateNif = new ValidateNif();
$this->assertTrue($validateNif->isValid('00000000T'));
}
}
Error : Class 'DojoValidateNifValidateNif' not found
/Users/franiglesias/PhpstormProjects/dojo/tests/Dojo/ValidateNif/ValidateNifTest.php:
13

16. Make the test pass
class ValidateNif
{
}
Error : Call to undefined method DojoValidateNifValidateNif::isValid()
/Users/franiglesias/PhpstormProjects/dojo/tests/Dojo/ValidateNif/ValidateNifTest.php:
14

17. Make the test pass
Failed asserting that null is true.
/Users/franiglesias/PhpstormProjects/dojo/tests/Dojo/ValidateNif/ValidateNifTest.php:
14
class ValidateNif
{
public function isValid(string $nif)
{
}
}

18. Make the test pass
OK (1 test, 1 assertion)
class ValidateNif
{
public function isValid(string $nif):bool
{
return true;
}
}

19. Hands on…

20. Fizz Buzz Kata
stage 1
Write a program that prints the numbers
from 1 to 100.
But for multiples of three print “Fizz”
instead of the number and for the
multiples of five print “Buzz”.
For numbers which are multiples of both
three and five print “FizzBuzz “.
http://codingdojo.org/kata/FizzBuzz/

21. Fizz Buzz Kata
stage 2
A number is “Fizz" if it is divisible by 3 or
if it has a 3 in it
A number is “Buzz” if it is divisible by 5 or
if it has a 5 in it
http://codingdojo.org/kata/FizzBuzz/

22. Fizz Buzz Kata
stage 3
We want all these rules configurable.
http://codingdojo.org/kata/FizzBuzz/