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Trisha Gee
Head of Developer Advocacy, Gradle
Are Your Tests
Slowing You Down?
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● Head of Developer Advocacy at Gradle
● Java Champion & JetBrains Community Contributor
● 20+ years development experience
● Author & YouTuber
Trisha Gee
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Tests Make You More
Productive?
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So it’s OK not to write tests,
right?
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Testing is Xanax for programmers, it’s an anxiety
reducing technique.”
https://youtu.be/guycIP56YeY
Kent Beck
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What slows down your testing?
Writing tests
Running tests locally
Running tests in CI
Troubleshooting tests
Unreliable test results
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1. Writing
2. Troubleshooting
3. Running
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1. Writing Tests Takes Time
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Use Your IDE
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AI Will Make You Super Productive
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AI is good for generating
mundane or predictable code
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AI is good for
generating test data
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AI can consider edge cases we
haven’t thought of
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AI can test what’s there. It can’t tell
you how the system should behave
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AI is a decent companion
…but it doesn’t replace you
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The keyboard is not the bottleneck.”
Dave Farley
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The productivity myth suggests that anything we
spend time on is up for automation…. The
importance and value of thinking about our work
and why we do it is waved away as a distraction.”
https://www.techpolicy.press/challenging-the-myths-of-generative-ai/
Eryk Salvaggio
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Bring a friend
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We recommend that the developers, who are good
at writing efficient, maintainable code, work
together with the testers, who are good at
specifying test cases, to automate tests.”
Agile Testing Condensed: A Brief Introduction
Lisa Crispin, Janet Gregory
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https://bit.ly/3RG85vc
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Creativity is a wild mind and a disciplined eye.”
Dorothy Parker
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Invest the time in writing to save
time troubleshooting
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2. Troubleshooting Takes Time
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What slows down your testing?
Writing tests
Running tests locally
Running tests in CI
Troubleshooting tests
Unreliable test results
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What is this test anyway?
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Your test needs to tell you
what is expected and why, so you
understand what to do when it fails.
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Why do tests fail?
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‣ Code is wrong
‣ Test is wrong
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Something changed
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• Production code
• Test code
• Refactoring/structure
• Data
• Infrastructure
• Load or usage
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1. Whose fault is it?
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1. Triage
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• Production code
• Test code
• Refactoring/structure
• Data
• Infrastructure
• Load or usage
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You need data
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2. Fix it
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Your best and wisest refuge from all troubles is in
your science.”
Ada Lovelace
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Learn how to use your debugger!
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Aim for fast feedback and
easy reproduction
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Fixed!
✅
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What slows down your testing?
Writing tests
Running tests locally
Running tests in CI
Troubleshooting tests
Unreliable test results
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“Unreliable test results”
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I have made the decision to trust you
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1. Find Your Flaky Tests
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This is not a fix!
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So now you can ignore those
flaky tests
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2. Quarantine your flaky tests
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3. Fix your flaky tests!!!
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If you add a new test and it’s flaky
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If you add a new test and it’s flaky
Or are working on a test and it
becomes flaky
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If you add a new test and it’s flaky
Or are working on a test and it
becomes flaky
Fix it now!!
(Future you will thank you)
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Make Time To Fix Flaky Tests
• When they impact you directly
• Attach them to related functionality
• Flaky Test Days
• Add flaky tests to the backlog
• 20% time, tech debt time, cleanup time…
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Causes of flakiness
1. Environment, Network, and Resources
2. Integration Points
3. Concurrency, Asynchronous Programming,
and Waiting
4. Setup/Teardown and Test Data
5. System Behaviour Known good practices and tools
Not always in my control
Try to minimise these
Can be REALLY HARD
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https://youtu.be/vHBzZHE4tJ0
1. Environment
2. Test Data
3. Versioning
4. Resource Use
5. System Behaviour
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3. Running Tests Takes Time
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What slows down your testing?
Writing tests
Running tests locally
Running tests in CI
Troubleshooting tests
Unreliable test results
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Use a Build Cache
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Spring Boot Build Times
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Very effective for
multi-module projects
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No cache: Full build required
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Build cache: Changing a module’s implementation
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Remote Build Cache
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Run tests in parallel (local)
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Run tests in parallel (CI)
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Test Distribution
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Test Distribution Results
‑ ~50%
‑ ~50%
‑ ~50%
Doubling the number of executors cuts build time in half
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Let’s use AI!
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The test selection procedure selects fewer than a
third of the tests that would be selected on the
basis of build dependencies”
Predictive Test Selection - Meta Research
https://research.facebook.com/publications/predictive-test-selection/
Mateusz Machalica, Alex Samylkin, Meredith Porth, Satish Chandra
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Predictive Test Selection time savings
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What if we just make our tests
faster?
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Like any performance problem,
focus on the worst first
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“Once things like databases become a hindrance, optimise
the testing loop, mock things out to run things fast. You can
run locally and you don't have all the same infra
dependencies as someone else.”
On DevEx, PaaS, and Testing in Production https://bit.ly/3ZA0uQM
Kelsey Hightower
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Look out for expensive setup and
tear down
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Invent Time Travel
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Write Better Tests
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• Separation of concerns
• Encapsulation
• High cohesion and loose coupling
• SOLID
• DRY
• Descriptive naming
• Modularisation
• Designing for performance
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Tension between these ideals
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Refactor and Delete
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“Yes, I regularly delete tests that no longer add unique
value.”
Angie Jones (@techgirl1908)
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In Summary
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Automate as much as possible
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Tooling can help you
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There is a time investment in writing tests,
because there should be thinking involved
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Invest time in writing better tests.
They will be easier to troubleshoot,
less flaky, and better document your
system’s expected behaviour
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Testing is not only for checking the system does
what it’s supposed to, it’s for documenting the
expected behaviour.”
Israel Boza Rodriguez (@IsraKaos)
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Thank you!
bit.ly/slow-tests
tinyurl.com/dv-trial
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