Project 2: Unit Testing Your grep

You will take the code from Project 1 and add unittest blocks to your functions, creating a self-testing codebase.

Quick Reference

Attribute Value
Primary Language D
Alternative Languages N/A
Difficulty Level 1: Beginner
Time Estimate A few hours.
Knowledge Area Software Engineering / Testing
Tooling dub
Prerequisites Project 1.

What You Will Build

You will take the code from Project 1 and add unittest blocks to your functions, creating a self-testing codebase.

Why It Matters

This project builds core skills that appear repeatedly in real-world systems and tooling.

Core Challenges

  • Writing a unittest block → maps to learning the simple syntax and how to use assert
  • Testing pure functions → maps to refactoring your code to make it more testable
  • Running tests with dub → maps to simply running dub test

Key Concepts

  • Unit Testing: “Programming in D” - Chapter 8.

Real-World Outcome

d unittest { string testContent = "line1\nError on line2\nline3"; auto results = findMatches(testContent, "Error"); assert(results.length == 1); assert(results[0].lineText == "Error on line2"); }

Implementation Guide

  1. Reproduce the simplest happy-path scenario.
  2. Build the smallest working version of the core feature.
  3. Add input validation and error handling.
  4. Add instrumentation/logging to confirm behavior.
  5. Refactor into clean modules with tests.

Milestones

  • Milestone 1: Minimal working program that runs end-to-end.
  • Milestone 2: Correct outputs for typical inputs.
  • Milestone 3: Robust handling of edge cases.
  • Milestone 4: Clean structure and documented usage.

Validation Checklist

  • Output matches the real-world outcome example
  • Handles invalid inputs safely
  • Provides clear errors and exit codes
  • Repeatable results across runs

References

  • Main guide: LEARN_D_PROGRAMMING_LANGUAGE.md
  • “Programming in D” by Ali Çehreli