Build Your Own Test Framework: A Practical Guide to Writing Better Automated Tests

Table of Contents
About the Author
About the Technical Reviewer
Acknowledgments
Foreword
Introduction
Chapter 1: Creating a Barebones Test Runner
    What Is an Entrypoint?
        The First Stage of Automated Test Enlightenment
        The Second Stage of Automated Test Enlightenment
    The Inner Workings of a Unit Test Runner
        The Third Stage of Automated Test Enlightenment
    Cloning the Project Repository
    Creating an NPM Project for the Test Runner
        Setting Package Configuration
    Creating the Test Runner Entrypoint
        Making the Package Available for Use
        Using the Sample Application Project
            npm unlink
        Update the Test Runner to Run Our Test Suite
    Verify That It Works by Breaking a Test
        Catch Exceptions from the Await Call
    Committing to Git
    Discussion Questions
    Summary
Chapter 2: Building a Function to Represent a Test Case
    The it Function
        Common Test Verbs
    Using the it Function to Group and Describe Test Cases
    Handling Exceptions
    Printing Test Descriptions
    Support CI with Correct Exit Codes
    Summarizing a Test Run
    Exercises
    Summary
Chapter 3: Grouping Tests
    The Basics of Unit Test Organization
    A Starting Point for describe
    Rethinking Test Output
        Printing a Pass/Fail Response for Each Test
        Ending a Test Report with Test Failure Details
    Saving Test Context Information
    Supporting Nested describe Blocks
    Exercises
    Summary
Chapter 4: Promoting Conciseness with Shared Setup and Teardown
    The Arrange, Act, Assert Pattern
        Arrange
        Act
        Assert
        Why Is This Pattern Important?
        Introducing the beforeEach Function
    Applying beforeEach Blocks to Our Test
        Refactoring describeStack to an Object
        Defining beforeEach
    Updating the Sample Application
    Defining afterEach
    Generalizing beforeEach
    Generalizing invokeBefores
    Exercise
    Discussion Question
    Summary
Chapter 5: Improving Legibility with Expectations and Matchers
    Using Matchers for Clarity and Reuse
    Building the First Matcher: toBeDefined
    Creating an Error Subtype
    Allowing Multiple Failures per Test
    Making a Mess
        Testing Your Solution
    Exercises
    Discussion Questions
    Summary
Chapter 6: Formatting Expectation Errors
    Utilizing Stack Traces with Testing Workflows
    Building stackTraceFormatter
    Joining Up Our Formatter with the Runner
    Exercises
    Discussion Questions
    Summary
Chapter 7: Automatically Discovering Test Files
    Development Workflows and Test Runners
        What About Watch Mode?
    Discovering Files
    Running a Single File
    Exercises
    Discussion Question
    Summary
Chapter 8: Focusing on Specific Tests
    The Refactor Workflow
    Introducing a Parse Step
    Implementing the Parse Phase
        Parsing the describe Function
        Adding the it Function
        Adding the beforeEach and afterEach Functions
    Implementing the Run Phase
        The Global currentTest Variable
    Updating the Runner
    Moving the expect Function
    Adding the Focus Functions
    Filtering Tests
    Exercises
    Discussion Question
    Summary
Chapter 9: Supporting Asynchronous Tests
    Event Loops in Runtime Environments
        Synchronicity and the Test Runner
        Waiting for Promise Completion
        Testing It Out
        Catching Exceptions
        Timing Out Tests After a Period of Time with the it.timesOutAfter Modifier
        Testing It Out
    Exercise
    Discussion Questions
    Summary
Chapter 10: Reporting
    The Observer Pattern, in a Half-Baked Style
        Adding an Event Dispatcher
        Dispatching a Begin Suite Event
        Dispatching a Test Finished Event
            Adding finishedTestRun
            Getting Rid of Failures and Successes
    Exercises
    Summary
Chapter 11: Shared Examples
    Methods of Reuse
        Implementing a Shared Example Repository
        Importing Shared Examples
    Exercise
    Discussion Questions
    Summary
Chapter 12: Tagging Tests
    Another Way of Slicing Tests
        Thinking Through Design Options
            Jest’s Approach
        Supporting Polymorphic Calls to Test Functions
        Filtering Test Runs Using the tags Property
        Reading Tags from the Process Arguments
        Adding Tags to the Sample Application
    Exercises
    Discussion Question
    Summary
Chapter 13: Skipping Tests
    Taming the Test Runner
    Adding the it.skip Modifier
    Testing It Out
    Supporting Empty-Body describe and it Calls
    Exercises
    Discussion Question
    Summary
Chapter 14: Randomizing Tests
    Test Runner Use Cases
        Randomizing Tests in CI Environments
        Randomizing Tests on Developer Machines
    Adding the Flag
        Testing It Out
    Exercises
    Discussion Question
    Summary
Chapter 15: Deep Equality and Constraining Matchers
    How Are Constraining Functions Useful?
    Implementing the equals Function
        Checking if Two Arrays Have Equal Size
        Checking if Two Objects Have Equal Keys
        Recursively Checking Element Equality
    Implementing the contains Constraint
    Exercises
    Discussion Questions
    Summary
Chapter 16: Test Doubles
    How Are Test Doubles Useful?
    Spies and Stubs
    Adding the New Tests
    Implementing the spy Function
    Implementing the toBeCalledWith Matcher
    Exercises
    Discussion Questions
    Summary
Chapter 17: Module Mocks
    How Are Module Mocks Useful?
    The Module Mock API
    Implementing the Mock Registry
    Implementing the Node Loader
        Adding the New Bin Script
    Bypassing the Module Cache
        Creating a Forwarding Reporter
        Defining the Worker Thread Entrypoint
        Updating the Test Runner to Use Worker Threads
        Changing Reported Test Objects to Be Serializable
    Exercises
    Discussion Question
    Summary