Test Driven Development: Workshop

@braddle Test Driven Development Workshop Mark Bradley | @braddle |
Sainsbury’s Group One | 02/10/2017

@braddle Code Repositories Java https://github.com/braddle/tdd-workshop-java PHP https://github.com/braddle/tdd-workshop-php Go https://github.com/braddle/tdd-workshop-go

@braddle Principal Software Engineer @ Sainsbury’s sporadic blogger @ mark-bradley.net
Husband to Miranda Father to Florence, Matilda & Rowan Collector ofCDs and Cook Books Mark Bradley

@braddle

@braddle What will we cover? • What is Test Driven
Development and why use it • The different types of tests • Writing our first tests • Refactoring • Test Doubles (Mocks, Stubs, Fakes, Spies, Dummies) • Test Quality

@braddle Warning: Audience Participation is expected and enforced

@braddle #E

@braddle

@braddle Pragmatic Dogmatic

@braddle What is Test Driven Development? • Writing tests before
you write code • Using tests to design how an application should work • Not just unit tests

@braddle Test First vs Test After

@braddle

@braddle Good Practices • Object Oriented Programming (OOP) ◦ Encapsulation
◦ Inheritance ◦ Polymorphism ◦ Interfaces • SOLID Principles ◦ Single Responsibility ◦ Open/Closed ◦ Liskov Substitution ◦ Interface Segregation ◦ Dependency Inversion • Hexagonal Architecture

@braddle If your tests are hard to write you design
is probably bad

@braddle Testing Pyramid End 2 End Integration Unit Test a
few parts of application together Uses mocked external dependencies Test a single function Use mocking for dependencies Only a few / possible only one test Run through the core journey Make use of actual external dependencies

@braddle Testing Pyramid End 2 End Integration Unit UI Test
Behavioural API Contract Tests ...

@braddle End to End Tests • Flows through you application
from start to finish • Uses all really services ◦ Database ◦ Email ◦ … • Only made up of one or two tests ◦ Core user journeys • May interact with many different parts of you app in a single test ◦ Customer applications ◦ Admin applications • May require some seeding of external services • Could be behavioural tests

@braddle Integration Tests • Tests a small number of units
together • Ensure the different units work together as expected • Mocks external dependencies ◦ Database ◦ Email ◦ …. • Could be behavioural Tests

@braddle Unit Tests • Tests a single unit/function (Targeted) •
Mocks any dependencies of the class and function (Isolated) • Unit test should be able to run over and over in any order without the result changing (Repeatable & predictable)

@braddle Other Types of Tests • API Contract Testing •
Security • Load (Volume and Performance)

@braddle The Test Driven Development Cycle 1. Write a test
2. Run tests (Latest test should fail || error) 3. Write code (Just enough code for the failing test to pass or error to go away) 4. Run test a. Test passed -> Continue b. Test Fails || New Error -> return to 3 5. Refactor (if required) REPEAT

@braddle Layered TDD Cycle

@braddle Why use Test Driven Development • Fewer defects in
your code • Only implement what is required • Increased code quality

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@braddle Unit Tests

@braddle TASK #1

@braddle Bug Report When I have an Integer and I
divide By 0. The universe implodes.

@braddle Refactoring

@braddle How do I test private methods?

@braddle TASK #2

@braddle Test Doubles • Imitating the functionality of dependencies •
Allowing for isolation of unit and integration tests • Do not necessarily require a mocking framework • Interfaces start becoming very important • Lots of different types of test double

@braddle Dummies

@braddle Stubs

@braddle TASK #3

@braddle Mocks

@braddle TASK #4

@braddle Spies

@braddle TASK #5

@braddle Fakes

@braddle TASK #6

@braddle TASK #7

@braddle Test Quality

@braddle Code Coverage

@braddle Mutation Testing Testing the your test by making changes
to the logic within the code you are testing. PHP: Humbug (https://github.com/humbug/humbug) Java: PIT (http://pitest.org/) Go: Mutesting (https://github.com/zimmski/go-mutesting)

@braddle Testing External Dependencies

@braddle TASK #8

@braddle Customer Satisfaction Project

@braddle Requirement #1 Feature: Customer Satisfation Index As A Store
Manager I want my customers to be able to give simple feedback on their shopping experience So that I can gage how changes I make to the store affect customer satisfaction Scenario: When a customer gives a positive feedback Then the customer should be thanked for their feedback And the positive feedback count should have increased by 1 Scenario: When a customer gives a negative feedback Then the customer should be thanked for their feedback And the negative feedback count should have increased by 1 Scenario: When a customer gives a neutral feedback Then the customer should be thanked for their feedback

@braddle Resources • 30 Days of TDD by James Bender
(@jamesbender) ◦ http://www.telerik.com/blogs/30-days-tdd-day-one-what-is-tdd • Code Coverage: Testing Private Functions (Me) ◦ http://mark-bradley.net/2017/03/11/code-coverage-testing-private-functions/ • SOLID Principles (Billie Thompson @PurpleBooth) ◦ https://purplebooth.co.uk/blog/2015/02/23/s-is-for-single-responsibility-principle/ • Speaker notes in these slides ◦ More in depth note about the slide ◦ Links to related articles

@braddle Feedback Twitter: @braddle Email: [email protected] Slide Deck: [Link]

@braddle Thank you

Test Driven Development: Workshop

Test Driven Development: Workshop

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