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Hands On Workshop: The Art of Unit Testing & TDD in Kotlin

with Roy Osherove

The Problem

Unit testing, done badly, can hurt your project more than it helps. In some cases, it may lead to project schedule delays, and unhappy developers due to huge maintenance problems. But when unit testing is done right, it can help the project and developers’ confidence immensely. The challenge is - how do you do it in a way that is helping, rather than hurting your project?

Objective

In this workshop we will learn essential test driven skills and techniques for writing unit tests in a readable, maintainable and trustworthy fashion, so that we can feel more confident in our code,  make it simpler, and save ourselves time in debugging and maintaining our code base. we will also look at some code design issues that hurt testability.

  1. Learn how to write readable, maintainable, trustworthy unit tests using Kotlin, JUnit 5, Kotlin-Test, mockk  and other unit testing tools and frameworks. 

  2. Learn how to refactor and test legacy code, and what to do when we cannot change existing code.

  3. Learn the principles of Test Driven Development, and develop new features using TDD.

  4. Learn how to Pair Program, and experience it throughout the course

  5. Learn about mocks, stubs fakes, and the difference between them

  6. Learn about Isolation(mocking) frameworks, how they work, and why some frameworks are more capable than others

Pre-Requisites

  • The course will benefit any developer with 1 year’s experience working with Kotlin

  • The course will mainly target Kotlin-JVM projects, but any kotlin target should be able to get value of out of this training

  • IntelliJ with Kotlin support required

Agenda

Day 1: Beginnings (09:00-16:00)

  1. What is the “unit” in “unit testing”? A discussion about unit of work.

  2. The first unit test

  3. Basic JUnit5 & Kotlin-Test APIs, test runners, tips and tricks

  4. Assertion Frameworks

  5. Writing readable tests

  6. Test Driven Development Introduction

  7. String Calculator  + Password Verifier Kata Exercises

  8. Value based,  State Based and Interaction Based Tests

Day 2: Mocks & Stubs (09:00-16:00)

  1. Understanding Fakes, Mocks and Stubs

  2. Hand Written Fakes, Stubs and Mocks

  3. Isolation Frameworks: mockk 

  4. Exercises

  5. Unit Testing Best Practices

  6. Code Review Exercises

Day 3: Diving Deeper (09:00-16:00)

  1. Refactoring Exercises:

    1. Faking Time

    2. Extract And Override

    3. Introduce Instance Delegator

  2. Exercises

  3. Reviewing tests from your own code

  4. Writing tests on your own production code (if time permits)

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