Tired of having users email you that your Svelte application is broken? Turns out that building reliable applications is hard and requires a lot of testing. You can write unit tests but quite often these all pass and the application is still broken. Why? Because they test parts of the application in isolation. But for a reliable application we need more. We need to make sure that all parts, including the backend API’s, work together as intended. Cypress is a great tool to achieve this. It will test you complete web application in the browser and use it like a real world user would. In this session Maurice will show you how to use Cypress during development and on the CI server with Svelte. He will share tips and tricks to make your tests more resilient and more like how an actual end user would behave.

1. Build reliableSvelte
applications usingCypress
Maurice de Beijer
@mauricedb
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2.  Maurice de Beijer
 The Problem Solver
 Microsoft MVP
 Freelance developer/instructor
 Twitter: @mauricedb
 Web: http://www.TheProblemSolver.nl
 E-mail: maurice.de.beijer@gmail.com
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3. Cypress.io
Course
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4. Topics
 What is Cypress.io?
 What is Svelte and SvelteKit?
 UsingTDD to building a SvelteKit application
 Testing pages
 API testing
 Running the Cypress tests in GitHub Actions
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5. What isCypress and
why should you care?
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6. Cypress.io
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7. What is
Cypress?
 Cypress is a front end testing tool
 Built for the modern web
 Tests are easy to write
 Using simple JavaScript orTypeScript
 TimeTravel runner lets you inspect test at each step
 Click on a step to see the state of the browser
 Automatic waiting for elements
 Makes tests more resilient
 Video recording of running test
 Helps debugging failing tests on the CI server
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8. What is
Cypress?
 Lets you fake the network when required
 Or use the real backend as appropriate
 Automatically retry of failing tests
 Run flaky tests multiple times
 Many standard and 3rd party extensions
 Or write your own in JavaScript
 Can run in Docker containers
 Consistent cross platform behavior
 Runs inside the browser
 Not based onW3C WebDriver API
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9. Testing
Triangle
🗣
End 2 End
Integration
UnitTesting
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10. UnitTesting
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11. Why End to End?
The more your tests resemble the way your software
is used, the more confidence they can give you!
Kent C. Dodds
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12. What isSvelte
andSvelteKit?
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13. svelte.dev
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14. Svelte
 A new approach to building user interfaces
 The most loved web framework according to Stack Overflow
 Svelte is a component framework
 Just like React,Vue or Angular
 A Svelte application is reactive
 Only the parts of the application that use reactive state are updated
 Compiles your components into JavaScript
 No Svelte runtime library
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15. SvelteKit
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16. SvelteKit
 SvelteKit is an application framework powered by Svelte
 Just like Next.js for React or Nuxt.js forVue
 Designed for building extremely high-performance web apps
 Server side rendering at runtime
 Prerendering at build time
 Prefetching pages
 File based routing
 HTTP API endpoints
 Error handling
 Sessions
 Very fast builds when developing
 UsingVite/ESBuild
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17. npm init svelte
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18. MovieCard.svelte
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19. What we are
building
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20. How we are
testing
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21. Cypress
Dashboard
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22. Cypress andTDD
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23. Testing the
navigation
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24. Testing anAPI
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25. Intercepting an
AJAX request
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26. GitHubAction
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27. CypressTesting Library
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28. 28

29. Cypress
Testing
Library
 Test your UI components in a more user-centric way
 Users don’t use CSS queries
 Allows better queries within Cypress
 Queries are often bases on accessibility
 SvelteTesting Library is also usable with Jest
 Using the same query functions
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30. Cypress
Testing
Library
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31. Code/Slides
 http://theproblemsolver.nl/Presentations
 https://github.com/mauricedb/surati-tech-talk-2022
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32. Conclusion
 Cypress is a great tool for End to End testing
 More reliable then relying on unit testing and manual testing
 Write tests that resemble your user’s actions
 Great approach forTest Driven Development
 Test that your API’s return the shape you expect
 A mismatch can lead to vague errors
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33. Maurice de Beijer
@mauricedb
maurice.de.beijer
@gmail.com
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