TDD

or: How I Learned to Stop Worrying and Love Tests

• story
• beginning - write for hours, hope it works

• incorrect assumptions
• errors
• hours hunting the bug

• not only that
• fix one thing - break another
• how do people do it with large programs??
• you must get better at this over time

Wiki: Test-driven development (TDD) is a software development process that relies on the repetition of a very short development cycle: first the developer writes an (initially failing) automated test case that defines a desired improvement or new function, then produces the minimum amount of code to pass that test, and finally refactors the new code to acceptable standards.

• simple process, hard to sum up
• what you want before how to do it

history

Kent Beck & XP

• 60s - mercury space program - punch card tdd
• 1999 - XP Explained
• 2002 - TDD By Example
• automated tests
• beck - sUnit - smalltalk
• beck - jUnit - java

history

2001: agile manifesto

• Uncle Bob, Martin Fowler, Alistair Cockburn, Kent Beck...
• heavyweight waterfall
• mid 90s - lightweight agile
• tdd -> xp -> agile

history

2001: agile manifesto

• value both sides
• how do you get to working software and embrace change?

waterfall

• throw over the wall
• you found a bug a month later?
• same day?

"Walking on water and developing software from a specification are easy if both are frozen." - Edward V Berard

• requirements change
• business doesn't know WHAT it wants until it's done
• devs don't know HOW to build it until it's done

agile

• evolve requirements over time - often
• deliver incrementally - often
• fail fast/often/small - cheaper
• embrace change

different levels of testing

• unit test
• integration test
• functional test
• acceptance test
• user test

exploratory testing, system testing, release testing...

• unit isolation / SRS
• integrate units
• functional (solution) - end to end
• acceptance (problem) - customer specs, given when then, black box
• (accept vs func) software is a solution to a problem
• Verification: Are we building the product right?
• Validation: Are we building the right product?
• definitions vary. test all levels

anantomy of a unit test

• setup
• prepare
• execute
• assert
• teardown

good unit test

• repeatable
• isolated
• automated

tdd

red green refactor

• unit - what, tdd - when
• beck - 10 mins or less, automatic
• REFACTOR - incremental (evolutionary) design
• code = creative writing
• uncle bob - test more specific -> code more generic
• regression
• JAVA EXAMPLE

BDD

Behaviour-Driven Development

Dan North

• where to start?
• what to test?
• how much to test in one go?
• what to name a test?
• why does the test fail?

• UK author
• too much emphasis no TEST
• not a testing technique, a design technique

BDD

semantics

test: calling the 'refresh' function reloads the item list array from the database

behavior: clicking the 'refresh' button should display the most recent item in the list

• north - JBehave - replacement for jUnit
• decoupling implementation (what from how)
• easier refactoring
• cross-team communication - common language
• bdd = tdd done right?
• JS EXAMPLE

tools

• xUnit
• Jasmine
• mock/fake/stub/spy

so, always tdd, right?

...depends on who you ask

• abstract logic into testable layers
• depends on task, team, experience
• price - more lines
• benefit (when done right) - modular decoupled codebase
• coverage is a nice side-effect

is tdd dead?

David Heinemeier Hansson (DHH) - April 2014 - TDD is dead. Long live testing.

Discussion with Martin Fowler and Kent Beck

• Rails, Basecamp
• problems: heavy mocking, cumbersome design
• ruby is too dynamic

summary

• one of core practices in Agile/XP
• unit test = what, tdd = when
• red - green - refactor
• bdd = tdd

?