Typescript TDD course in 4 parts

readme.md

Intro to TypeScript for JavaScript Developers with Test-Driven Development (TDD)

Course Overview

This course introduces JavaScript developers to TypeScript while emphasizing Test-Driven Development (TDD). It focuses on leveraging TypeScript's static typing and tooling to improve software reliability and maintainability.

Prerequisites

• Familiarity with JavaScript (ES6+)
• Basic understanding of unit testing (Jest, Mocha, or similar)

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Week 1: Introduction to TypeScript & Setting Up a TDD Workflow

Learning Objectives

• Understand the benefits of TypeScript over JavaScript
• Set up a TypeScript project with Jest for TDD
• Write basic TypeScript with type annotations

Topics Covered

• What is TypeScript? Why use it?
• Setting up TypeScript (tsc, tsconfig.json)
• Installing and configuring Jest with TypeScript
• Writing and running a basic test in TypeScript
• Type annotations (number, string, boolean, any, unknown)
• First TDD cycle: Write a test → Write minimal TypeScript → Refactor

Exercise

1. Initialize a TypeScript project with Jest.
2. Write a function add(a, b): number following TDD principles.

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Week 2: Functions, Interfaces, and Testing Strategies

Learning Objectives

• Understand TypeScript’s function signatures and parameter types
• Learn about interfaces and how they enforce contracts
• Explore testing strategies for functions and objects

Topics Covered

• Function signatures (optional, default, rest parameters)
• Defining and using interfaces
• Testing pure functions in TypeScript
• Using tsc --noEmit for type-checking without compilation
• Error handling and testing edge cases

Exercise

1. Create an interface for a User object.
2. Write a function getFullName(user: User): string and test it using TDD.

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Week 3: Classes, Enums, and Dependency Injection in TDD

Learning Objectives

• Learn how to use TypeScript classes
• Understand enum usage in TypeScript
• Implement dependency injection for better testability

Topics Covered

• TypeScript class and constructor parameters
• Public, private, and readonly properties
• Using enum for managing constant values
• Mocking dependencies in unit tests
• Testing class methods using Jest

Exercise

1. Create a Logger class with a logMessage(level: LogLevel, message: string) method.
2. Use TDD to build and test the class.

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Week 4: Advanced TypeScript & Real-World TDD Practices

Learning Objectives

• Explore generics and how they improve code reusability
• Understand TypeScript’s utility types
• Learn how to integrate TypeScript and TDD in a real-world project

Topics Covered

• Generics (T, U, K extends keyof T)
• TypeScript utility types (Partial<T>, Readonly<T>, Pick<T>)
• Testing asynchronous code and promises in TypeScript
• Integrating TypeScript into an existing JavaScript project
• Using ESLint and Prettier for TypeScript projects

Exercise

1. Create a fetchData<T>(url: string): Promise<T> function.
2. Write tests to ensure proper error handling and response parsing.

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Final Project

Participants will apply their knowledge by developing a small, test-driven TypeScript application, such as:

• A simple to-do list with TypeScript classes and interfaces
• A REST API client with typed responses and unit tests
• A CLI tool using TypeScript and Node.js

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Course Wrap-Up

• Review key takeaways from TypeScript and TDD
• Discuss real-world use cases and best practices
• Provide resources for further learning

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Additional Resources

• Official TypeScript Docs: https://www.typescriptlang.org/docs/
• Jest Docs: https://jestjs.io/docs/en/getting-started
• TypeScript Handbook: https://www.typescriptlang.org/docs/handbook/intro.html