Testing JavaScript Applications

Testing JavaScript Applications
contents
preface
acknowledgments
about this book
Who should read this book
How this book is organized: A roadmap
About the code
System requirements
liveBook discussion forum
about the author
about the cover illustration
Part 1 Testing JavaScript applications
1 An introduction to automated testing
1.1 What is an automated test?
1.2 Why automated tests matter
1.2.1 Predictability
1.2.2 Reproducibility
1.2.3 Collaboration
1.2.4 Speed
Summary
2 What to test and when?
2.1 The testing pyramid
2.2 Unit tests
2.3 Integration tests
2.4 End-to-end tests
2.4.1 Testing HTTP APIs
2.4.2 Testing GUIs
2.4.3 Acceptance tests and end-to-end tests are not the same
2.5 Exploratory testing and the value of QA
2.6 Tests, cost, and revenue
Summary
Part 2 Writing tests
3 Testing techniques
3.1 Organizing test suites
3.1.1 Breaking down tests
3.1.2 Parallelism
3.1.3 Global hooks
3.1.4 Atomicity
3.2 Writing good assertions
3.2.1 Assertions and error handling
3.2.2 Loose assertions
3.2.3 Using custom matchers
3.2.4 Circular assertions
3.3 Test doubles: Mocks, stubs, and spies
3.3.1 Mocking imports
3.4 Choosing what to test
3.4.1 Don’t test third-party software
3.4.2 To mock, or not to mock: That’s the question
3.4.3 When in doubt, choose integration tests
3.5 Code coverage
3.5.1 Automated coverage reports
3.5.2 Coverage types
3.5.3 What coverage is good for and what it isn’t
Summary
4 Testing backend applications
4.1 Structuring a testing environment
4.1.1 End-to-end testing
4.1.2 Integration testing
4.1.3 Unit testing
4.2 Testing HTTP endpoints
4.2.1 Testing middleware
4.3 Dealing with external dependencies
4.3.1 Integrations with databases
4.3.2 Integrations with other APIs
Summary
5 Advanced backend testing techniques
5.1 Eliminating nondeterminism
5.1.1 Parallelism and shared resources
5.1.2 Dealing with time
5.2 Reducing costs while preserving quality
5.2.1 Reducing overlap between tests
5.2.2 Creating transitive guarantees
5.2.3 Turning assertions into preconditions
Summary
6 Testing frontend applications
6.1 Introducing JSDOM
6.2 Asserting on the DOM
6.2.1 Making it easier to find elements
6.2.2 Writing better assertions
6.3 Handling events
6.4 Testing and browser APIs
6.4.1 Testing a localStorage integration
6.4.2 Testing a History API integration
6.5 Dealing with WebSockets and HTTP requests
6.5.1 Tests involving HTTP requests
6.5.2 Tests involving WebSockets
Summary
7 The React testing ecosystem
7.1 Setting up a test environment for React
7.1.1 Setting up a React application
7.1.2 Setting up a testing environment
7.2 An overview of React testing libraries
7.2.1 Rendering components and the DOM
7.2.2 React Testing Library
7.2.3 Enzyme
7.2.4 The React test renderer
Summary
8 Testing React applications
8.1 Testing component integration
8.1.1 Stubbing components
8.2 Snapshot testing
8.2.1 Snapshots beyond components
8.2.2 Serializers
8.3 Testing styles
8.4 Component-level acceptance tests and component stories
8.4.1 Writing stories
8.4.2 Writing documentation
Summary
9 Test-driven development
9.1 The philosophy behind test-driven development
9.1.1 What test-driven development is
9.1.2 Adjusting the size of your iterations
9.1.3 Why adopt test-driven development?
9.1.4 When not to apply test-driven development
9.2 Writing a JavaScript module using TDD
9.3 Testing top-down versus testing bottom-up
9.3.1 What bottom-up and top-down testing mean
9.3.2 How top-down and bottom-up approaches impact a test-driven workflow
9.3.3 The pros and cons of bottom-up versus top-down approaches
9.4 Balancing maintenance costs, delivery speed, and brittleness
9.4.1 Test-driven implementation
9.4.2 Test-driven maintenance
9.5 Setting up an environment for TDD to succeed
9.5.1 Teamwide adoption
9.5.2 Keeping distinct lanes
9.5.3 Pairing
9.5.4 Supplementary testing
9.6 TDD, BDD, validations, and specificationsBDD (behavior-driven development)
Summary
10 UI-based end-to-end testing
10.1 What are UI-based end-to-end tests?
10.2 When to write each type of test
10.2.1 UI-based end-to-end tests
10.2.2 Pure end-to-end tests
10.2.3 Pure UI tests
10.2.4 A note on acceptance testing and this chapter’s name
10.3 An overview of end-to-end testing tools
10.3.1 Selenium
10.3.2 Puppeteer
10.3.3 Cypress
10.3.4 When to choose Cypress
Summary
11 Writing UI-based end-to-end tests
11.1 Your first UI-based end-to-end tests
11.1.1 Setting up a test environment
11.1.2 Writing your first tests
11.1.3 Sending HTTP requests
11.1.4 Sequencing actions
11.2 Best practices for end-to-end-tests
11.2.1 Page objects
11.2.2 Application actions
11.3 Dealing with flakiness
11.3.1 Avoiding waiting for fixed amounts of time
11.3.2 Stubbing uncontrollable factors
11.3.3 Retrying tests
11.4 Running tests on multiple browsers
11.4.1 Using a testing framework to run tests within a browser
11.4.2 Running UI-based tests in multiple browsers
11.5 Visual regression tests
Summary
Part 3 Business impact
12 Continuous integration and continuous delivery
12.1 What are continuous integration and continuous delivery?
12.1.1 Continuous integration
12.1.2 Continuous delivery
12.2 The role of automated tests in a CI/CD pipeline
12.3 Version-control checks
Summary
13 A culture of quality
13.1 Using type systems to make invalid states unrepresentable
13.2 Reviewing code to catch problems machines can’t
13.3 Using linters and formatters to produce consistent code
13.4 Monitoring your systems to understand how they actually behave
13.5 Explaining your software with good documentation
Summary
index
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