TDD in JavaSCRIPT
Name: Yoan Ribeiro
Title: Full-Time Learner
Works @ JS-Republic
@yoanribeiro
Yoanribeiro
SUMMARY
- Unit Testing
- The concept
- Demo
- Pros/cons
TDD = Unit TESTING
You make unit test by using TDD but make unit test is not necessary using TDD
Unit TESTING
when you test a small part of code isolated from the rest.
(e.g. function or class)
UNIT TESTING - RULES
- AUTOMATIC
- VERY FAST (<300ms)
- ISOLATED (no side effect)
- VERIFY A SMALL UNIT
Unit testing - JS FLAVOR Example
Take, the example of a function responsible of returning the number of specific dom elements.
We will use Mocha as test runner
Chai as assertion library
Unit testing - JS FLavor EXAMPLE
REMEMBER : Given WHEN THEN
Prepare the case you want to test
REMEMBER : Given WHEN THEN
Call what you want to test
REMEMBER : Given WHEN THEN
Verify the behavior, result of what you test
REMEMBER : Given WHEN THEN
The three parts of every unit test
Test DRIVEN DEVELOPMENT
First test your use case, then implement your use case, refactor and start over until functionality is over.
TDD, AN OLD STORY
1957 - Digital Computer Programming, D.D. MCCRACKEN
1968 - Report of The Nato Software Engineering Conference, P. Naur
1972 - The Humble Programmer, Edsger W. Dijkstra
2000 - Test-Driven Development by Example , Kent Beck
TDD is A methodology
TDD = Write all your testS first
TDD is A CYCLE
Red
Green
REFACTOR
Red / Green / Refactor
Write a test
which fails
Refactor by keeping it green
Make the test
pass
Write a unit test which test a case not yet implemented. Obviously, this test will failed !
It's what we want
Red / Green / Refactor
Write a test
which fails
Refactor by keeping it green
Make the test
pass
Write an implementation which resolve the case that you just test (and the previous test cases) and no more
Red / Green / Refactor
Write a test
which fails
Refactor by keeping it green
Make the test
pass
Refactor to improve the general implementation by keeping every use case green.
Red / Green / Refactor
Write a test
which fails
Refactor by keeping it green
Make the test
pass
DEMO
Pros
- Better code coverage
- Better architecture (less coupling)
- Gives us a degree of certainty
CONS
- Require good understanding of the used technology
- Can be a little bit time consuming at the beginning
CONCLUSION
TDD is nice to increase quality
TDD should not be a dogma
To make unit tests every single time is already good thing
https://github.com/Yoanribeiro/tdd-js-star-april
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