A presentation at DDD Melbourne 2024 in in Melbourne VIC, Australia by Julian Burr
MELBOURNE2024 “IS IT A BIRD? IS IT A PLANE?” THE WEIRD SHAPES WE USE TO TALK ABOUT TESTING
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MELBOURNE2024 “IS IT A BIRD? IS IT A PLANE?” THE WEIRD SHAPES WE USE TO TALK ABOUT TESTING
PART I: Common testing methodologies
THE DIFFERENT TYPES OF TESTS
THE DIFFERENT TYPES OF TESTS
THE DIFFERENT TYPES OF TESTS com bin un ati its o big t ger hat n of ser buil vic d es
https://www.reddit.com/r/ProgrammerHumor/comments/isidkn/unit_testing_vs_integration_testing/
THE DIFFERENT TYPES OF TESTS
THE DIFFERENT TYPES OF TESTS
THE DIFFERENT TYPES OF TESTS
“THE SHAPES”
“THE SHAPES” — THE PYRAMID e2e integration unit https://web.dev/articles/ta-strategies
“THE SHAPES” — THE PYRAMID more integrated e2e integration more isolated unit https://web.dev/articles/ta-strategies
“THE SHAPES” — THE PYRAMID slower & more expensive e2e integration faster & cheaper unit https://web.dev/articles/ta-strategies
“THE SHAPES” — THE ICE CONE e2e integration unit https://web.dev/articles/ta-strategies
“THE SHAPES” — THE CRAB 🦀 e2e integration & unit tests https://web.dev/articles/ta-strategies
“THE SHAPES” — THE DIAMOND e2e integration unit https://web.dev/articles/ta-strategies
“THE SHAPES” — THE DIAMOND e2e integration unit https://web.dev/articles/ta-strategies
“THE SHAPES” — THE HONEYCOMB e2e integration unit https://web.dev/articles/ta-strategies
WE ARE ABLE TO REFACTOR THE INTERNALS WITHOUT TOUCHING ANY TESTS. WE COULD EVEN REPLACE THE DATABASE FROM POSTGRESQL TO NOSQL WITHOUT HAVING TO MODIFY THE ACTUAL TEST METHODS. https://engineering.atspotify.com/2018/01/testing-of-microservices/
THE TRADE-OFF HERE IS SOME LOSS OF SPEED IN TEST EXECUTION [… AND …] THAT WE MIGHT LOSE SOME FEEDBACK ACCURACY WHEN A TEST FAILS https://engineering.atspotify.com/2018/01/testing-of-microservices/
“THE SHAPES” — THE TROPHY e2e integration unit static https://web.dev/articles/ta-strategies
https://twitter.com/searls/status/1393571227650908162
https://twitter.com/searls/status/1393385209089990659
PART II: Why do we write tests?
PART II: Why do we not write tests?
WHY DO WE NOT WRITE TESTS?
WHY DO WE NOT WRITE TESTS? “We don’t have time for this”
WHY DO WE NOT WRITE TESTS? “We don’t have time for this” “They start failing when changing unrelated code or implementation details and are becoming brittle quickly”
WHY DO WE DO WRITE TESTS?
WHY DO WE DO WRITE TESTS? “To make our managers or team lead happy”
ANY OBSERVED STATISTICAL REGULARITY WILL TEND TO COLLAPSE ONCE PRESSURE IS PLACED UPON IT FOR CONTROL PURPOSES — Goodhart’s Law https://www.ribbonfarm.com/2016/06/09/goodharts-law-and-why-measurement-is-hard/
WHY DO WE DO WRITE TESTS? “To make our managers or team lead happy”
WHY DO WE DO WRITE TESTS? “To make our managers or team lead happy” Stability for the end-user
“A MAJORITY OF THE PRODUCTION FAILURES (77%) CAN BE REPRODUCED BY A UNIT TEST.” — Simple testing can prevent most critical failures; Research paper from the University of Toronto (2014) https://www.usenix.org/system/files/conference/osdi14/osdi14-paper-yuan.pdf
WHY DO WE DO WRITE TESTS? “To make our managers or team lead happy” Stability for the end-user Enable refactoring
CODE IS READ AND UPDATED WAY MORE OFTEN THAN IT IS WRITTEN — Tim Bray https://www.tbray.org/ongoing/When/202x/2021/05/15/Testing-in-2021
“WALKING ON WATER AND DEVELOPING SOFTWARE FROM A SPECIFICATION ARE EASY IF BOTH ARE FROZEN” — Edward V. Berard https://en.wikiquote.org/wiki/Edward_V._Berar
PART III: a little d etour, sorry! TDD — The misunderstood monster under your bed
RED-GREEN-REFACTOR
RED-GREEN-REFACTOR Write a test that describes the desired behaviour https://tidyfirst.substack.com/p/canon-tdd
RED-GREEN-REFACTOR Write a test that describes the desired behaviour Write the minimal amount of code necessary to make the test pass https://tidyfirst.substack.com/p/canon-tdd
RED-GREEN-REFACTOR Write a test that describes the desired behaviour Write the minimal amount of code necessary to make the test pass Refactor the code https://tidyfirst.substack.com/p/canon-tdd
SELF-TESTING CODE
SELF-TESTING CODE Tests should be part of your code delivery https://martinfowler.com/distributedComputing/duckling.pdf
SELF-TESTING CODE Tests should be part of your code delivery You should be running tests as often as possible — ideally automated https://martinfowler.com/distributedComputing/duckling.pdf
TDD — SOME MISCONCEPTIONS
TDD — SOME MISCONCEPTIONS “TDD means I have to write my tests first!”
IS TDD DEAD? — VIDEO SERIES WITH DHH, MARTIN FOWLER AND KENT BECK https://martinfowler.com/articles/is-tdd-dead/
TDD — SOME MISCONCEPTIONS “TDD says I have to mock everything outside of the unit test scope”
“SIMILARLY THEIR NOTION OF INTEGRATION TEST SOUNDS VERY MUCH LIKE WHAT I WOULD CALL A SOCIABLE UNIT TEST. THIS MAKES THE PYRAMID VERSUS HONEYCOMB DISCUSSION MOOT” — Martin Fowler https://martinfowler.com/articles/2021-test-shapes.html
PART IV: Practical tips to get started with testing
1 Be the advocate!
2 Embrace tests as a way to improve developer confidence
3 Test behaviour, not implementation details
4 Automate your tests!
5 Identify the most common or likely points of failure in your system
ANOTHER APPLICATION OF CYCLOMATIC COMPLEXITY IS IN DETERMINING THE NUMBER OF TEST CASES THAT ARE NECESSARY TO ACHIEVE THOROUGH TEST COVERAGE OF A PARTICULAR MODULE. https://en.wikipedia.org/wiki/Cyclomatic_complexity
6 Don’t just blindly follow a “shape” or strategy
ENSURE YOUR “SHAPE” HAS INTENTION
ENSURE YOUR “SHAPE” HAS INTENTION let’s add the static la yer
ENSURE YOUR “SHAPE” HAS INTENTION m e t s y s eco e m o s s r e v o c s t s te
ENSURE YOUR “SHAPE” HAS INTENTION m e t s y s eco e m o s s r e v o c s t s te other “natur al” erosio n
7 Have smaller milestones to work towards the end goal
MILESTONES TO YOUR IDEAL SETUP manual testing
MILESTONES TO YOUR IDEAL SETUP quick & easy confid ence boost
MILESTONES TO YOUR IDEAL SETUP p u g n i d l i e r bu o c e h t
MILESTONES TO YOUR IDEAL SETUP
THE END. @jburr90 / Julian Burr https://www.julianburr.de/ ddd-melbourne-2024-slides.pdf
Proudly sponsored by MELBOURNE2024 Diamond Sponsors Platinum Sponsors Gold Sponsors Childcare by: Wi-Fi by: Coffee Cart by: Silver Sponsors
MELBOURNE 2024
Pyramids, trophies, ice cream cones, diamonds, you name it. There are a lot of things we use to describe our approaches to testing, and it can be hard sometimes to see through the metaphors to understand which one is the best.
The reality is that there is no one-size-fits-all solution to testing. Instead, let’s have a deeper look at the current landscape of testing methodologies and the nuances of its layers. What do they have in common? What are the differences? And how do you choose the right elements for your unique circumstances?
