Presentation about TDD on the GDCR 2016 event organized at the ThoughtWorks South Africa offices

1. Test Driven
Development

2. Test Driven
Development
 Technique to design and develop software.
 Practice part of the Extreme Programming methodology — XP
 Based on three fundamental pillars.

3. TheThree
Pillars
 Implement the exact
functionality of the software.
 Reduce the number of defects
on the software – good quality
software
 Produce modular and highly
reusable software.

4. When Doing
TDD
 It’s not about just writing tests.
 Translate use cases to examples.
 Enough to describe the functionality without ambiguity.
 Architecture will eventually emerge.

5. TheTDD
Algorithm
Red
GreenRefactor

6. TheTDD
Algorithm
Red
GreenRefactor

7. TDD InAction
With an example ;-)

8. The Problem Email validation mechanism

9. The Problem
Email validation mechanism

10. The Problem
Email validation mechanism
Neither empty nor null.
Has to contain an @ symbol
Has to belong to the .com, .net and .eduTDLs
Domain part can’t be 1 character long
All lowercase
Not contain numbers
Only _ . - symbols

11. Before we
begin
WritingTests
 Testing framework
 Part of the language
 Ruby
 Rust
 Go
 Python
 External tools and libraries
TestNG
MSTest

12. Neither empty nor null
Red
@Test
public void shouldReturnFalseIfEmailIsNull() {
String email = null;
EmailValidator validator = new EmailValidator();
boolean isValid = validator.isValid(email);
assertThat(isValid, equalTo(false));
}

13. Neither empty nor null
Green public boolean isValid(String email) {
return false;
}

14. Neither empty nor null
Red
@Test
public void shouldReturnTrueIfEmailLengthIsGreaterThanZero() {
String email = "some@email.com";
EmailValidator validator = new EmailValidator();
boolean isValid = validator.isValid(email);
assertThat(isValid, equalTo(true));
}

15. Neither empty nor null
Green
public boolean isValid(String email) {
if (email == null) {
return false;
}
return email.length() > 0;
}

16. Contains an @ symbol
Red
@Test
public void shouldReturnFalseIfEmailDoesntContainAtSymbol () {
String email = "someemail.com";
EmailValidator validator = new EmailValidator();
boolean isValid = validator.isValid(email);
assertThat(isValid, equalTo(false));
}

17. Neither empty nor null
Green
public boolean isValid(String email) {
if (email == null) {
return false;
}
if (!email.contains("@")) {
return false;
}
return email.length() > 0;
}

18. Refactor
private EmailValidator validator;
@Before
public void setUp () {
validator = new EmailValidator();
}

19. In the end…
 Components will behave exactly as we want.
 Tests will be the documentation of our system.
 Tests will break if changes compromise the system.

20. Thank you!
Carlos Andrés Oquendo
coquendo@thoughtworks.com
@andres19_05