In this module, you’ll learn how to use Nullables to create fast, reliable tests of application-level code that depends on infrastructure. You’ll test-drive the implementation of HomePageController, the controller for a web page that uses a ROT-13 microservice to encode the user’s text.

Concepts

Download the slides and transcript here.

Direct links to patterns discussed in this module:

• Narrow Tests
• State-Based Tests
• Overlapping Sociable Tests
• Signature Shielding
• Parameterless Instantiation
• Nullables
• Configurable Responses
• Output Tracking
• Behavior Simulation

Primers

You may wish to familiarize yourself with these primers before starting on the exercises:

• JavaScript Basics
• Introduced in challenge #1:
  • await
• Introduced in challenge #4:
  • async
  • Object Shorthand
  • Object Destructuring
  • Default Function Parameters
  • String Interpolation
• Introduced in challenge #9:
  • Using Promises
  • Rest Operator (...)
  • Spread Operator (...)
  • Arrow Functions

Exercise Setup

Start with the Pre-Course Setup. Then:

1. Check out the code

1. Check out the exercise branch:
   • JavaScript: git checkout using-nullables-js
   • TypeScript: git checkout using-nullables-ts
2. Create a custom branch for your changes:
   • git checkout -b my-using-nullables

2. Prepare to start working

1. Open the exercise files:
   • src/www/home_page/_home_page_controller_test.js (or .ts)
   • src/www/home_page/home_page_controller.js (or .ts)
2. Run the build watcher from the root of the repository:
   • Windows: .\watch.cmd quick
   • Mac/Linux: ./watch.sh quick
3. Confirm that the build runs and ends with BUILD OK.

Exercises

The course is designed to have more exercises than you can finish in a single session, so don’t worry about finishing everything. Instead, work at your own pace and focus on understanding the material. If you get to the end of challenge #3, you’ll have covered the most important information.

1. Challenge #1: Using Nullables
2. Challenge #2a: Tracking Requests
3. Challenge #2b: Dynamic Configuration
4. Challenge #2c: Parsing the Request Body
5. Challenge #3: Configuring Responses
6. Challenge #4: Signature Shielding
7. Challenge #5: Logging
8. Challenge #6: Refactoring
9. Challenge #7: Service Errors
10. Challenge #8: Design Changes
11. Challenge #9: Timeouts
12. Bonus Challenges

Start with Challenge #1

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