Test-driven development

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Neil Hodge
5 years ago
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1 Test-driven development And how we do it at WIX Mantas Indrašius Software Engineer WIX.COM

2 Agenda Tests overview Test-driven development (TDD) Let s see it in action (demo) Kickstarting a project using TDD How we do it in WIX

3 Tests overview

4 Why writing tests Reliability Freedom of change Tests as specification Design hints for free Saves time and cost Instant/fast feedback

5 Developer feedback

6 Feedback cycles Unit tests - a second or two Acceptance test minutes Manual testing / using debugger minutes Continuous integration minutes Peer review - few hours QA - from few hours to days Production - days, weeks or months And we do it in multiple iterations

7 Feedback from process

8 The Word of Wisdom Fail as fast as you can!

9 Levels of testing Acceptance - does the whole system work? Integration - does our code work with 3rd party? Unit - do our objects do the right thing?

10 Pyramid of developer tests

11 Unit tests We set requirements for object behavior We set preconditions and expectations Test behavior with different input arguments We use object mocks to isolate the class under test

12 Unit tests

13 Unit tests

14 Acceptance testing

15 TDD (Test-driven development)

16 What is TDD? It s a development process of very short development cycles based on a rapid feedback It s a design activity It s a design support tool It s a safety net of regression coverage

17 The basics of TDD process Write a test Run all tests and see the new one fails Write minimal amount of code for the test to pass Run all the tests and see them pass Refactor code to acceptable standards

18 Red - Green - Refactor

19 The Golden Rule of TDD Never write a new functionality without a failing test

20 The Bigger Picture Write a failing acceptance test and keep it so Go to the class level and do TDD with unit and/or integration tests Once finished, check the acceptance test If it s still not passing, continue with changes in the class level

21 The Bigger Picture

22 Let s see it in action Demo

23 Why acceptance tests are not enough Acceptance tests are slow They are not suitable to test edge cases They don t help maintaining a good design They are not allowed to have access to the internal components of the system

24 How TDD helps us? We learn to grow software incrementally We learn to design in top-down approach We write just enough code for a feature We are guided to maintain a sustainable design We don t need UML in software design At any given time we have a ready to deploy system We always have the most up-to-date specification

25 Agile loves TDD Incremental development Short feedback loop Working software over documentation There is no component someone owns Quality first

27 Kickstarting a project Using TDD

28 The first step: The Walking Skeleton The Goal: Build the infrastructure Choose the minimal system feature to focus on infrastructure Infrastructure should include all the essential anticipated components We should learn how to build and deploy Pass the first acceptance test

29 The Walking Skeleton on legacy The Goal: Build the infrastructure Choose the simplest existing system feature and focus on building the infrastructure Infrastructure should include all the essential anticipated components Pass the first acceptance test Cover the other cases one-by-one

30 The context of the first step

31 Uncertainty in test-first and testlater

32 How we do it in WIX

33 What do we do in WIX Website editing and publishing platform User account / business management system App Market Hundreds of small applications in the market Business verticals: hotels, reservations, music, photography etc

34 Scale of WIX More than 57,000,000 users 1.2PB of data (1.5TB per day) 900 servers in 3 data centers 3 clouds (Google, Amazon, Azure) dynamic requests per minute More than 900 employees

35 Engineering in WIX WIX is a company with developer-centric approach Excellence of Engineering is our priority to adding new features Every developer in WIX is also a DevOp Service oriented architecture We do continuous delivery

36 TDD at WIX We believe in TDD, we start learning it from the first day at work Client-side and server-side do it separately in their isolated ecosystems We approach TDD from E2E rather than acceptance testing TDD empowers us to practice the Continuous delivery approach

37 Continuous delivery

38 Our Concerns Continuous integration Backwards and forwards compatibility Feature oriented design Experiments Data inconsistency

39 Tools TeamCity - continuous integration and release LifeCycle - a custom built tool to manage the project lifecycles (version management, delivery) Artifactory - storage for artifacts Chef - deployments / server provisioning

40 Client-side infrastructure AngularJS for building the rich UI Grunt for running the build (incl. tests) Jasmine for describing test behavior Karma + PhantomJS for testing units Selenium with Protractor for E2E or acceptance tests SauceLabs for cross-platform testing

41 Client-side build Run the unit tests with Karma & PhantomJS Start a fake API server on NodeJS Start the controlled browsers Run the E2E test suite against them Clean up & deliver the artifact

42 Server-side infrastructure Scala/Java for server applications Maven as a build tool specs2/junit for describing the test behavior JMock/Mockito for testing units Custom HTTP test-kit for HTML/JSON matching

43 Server-side build Run unit tests Setup the embedded environment (MySQL, MongoDB, Cassandra) Start the fake 3rd party services Start the server under test Run the E2E test suite against it Clean up & deliver the artifact

44 Release process in WIX

45 Ačiū! Any Questions?

Test-driven development

Test-driven development And how we do it at WIX Mantas Indrašius Software Engineer WIX.COM Agenda Tests overview Test-driven development (TDD) The Bowling Game demo Kickstarting a project using TDD How