Exercise Guide

This project includes exercises in 4 languages — TypeScript, Rust, Go, and Python. Each pattern has at least one exercise per language with working implementations and TODO markers for you to rewrite.

Prerequisites

Language	Required Version	Install
Node.js	v22 LTS	nvm or nodejs.org
Rust	stable (latest)	rustup.rs
Go	1.21+	go.dev/dl
Python	3.10+	python.org or system package manager

Quick Start

# Clone the repository
git clone https://github.com/Totoro-jam/battle-tested-patterns.git
cd battle-tested-patterns

# Use the correct Node.js version
nvm use   # reads .nvmrc → Node 22

Setup by Language

TypeScript

# Install dependencies (one time)
pnpm install

# Run all TypeScript exercises
pnpm test:exercises

# Run a specific pattern
pnpm test:exercises bitmask

# Watch mode — re-runs on file save
pnpm test:exercises -- --watch

File location: exercises/typescript/<pattern-name>/01-basic.test.ts

Each pattern has 1–3 exercise files by difficulty level (01-basic, 02-intermediate, 03-advanced).

Rust

# No extra install needed — Cargo handles everything

# Run all Rust exercises
cd exercises/rust
cargo test

# Run a specific pattern
cargo test bitmask

# Run with output visible
cargo test bitmask -- --nocapture

File location: exercises/rust/src/<pattern_name>/mod.rs

Each file contains the implementation and tests in a single module with #[cfg(test)].

Go

# No extra install needed — Go modules handle dependencies

# Run all Go exercises
cd exercises/go
go test ./...

# Run a specific pattern
go test -run Bitmask -v ./...

# Run with verbose output
go test -v ./...

File location: exercises/go/<pattern_name>/<pattern_name>_test.go

Each file contains both the implementation and test functions in the same package.

Python

# Install pytest (one time)
pip install pytest

# Run all Python exercises
cd exercises/python
pytest

# Run a specific pattern
pytest bitmask/test_bitmask.py

# Run with verbose output
pytest -v

File location: exercises/python/<pattern_name>/test_<pattern_name>.py

Each file is self-contained — no cross-file imports.

How Exercises Work

Every exercise follows the TODO-stub format:

1. Functions have working implementations (so CI always passes)
2. // TODO: implement markers indicate lines for you to rewrite
3. Tests below the separator line are immutable — don't modify them
4. Delete the function body, implement from scratch, run the tests

Example workflow

# 1. Pick a pattern — say, ring-buffer
# 2. Open the exercise file in your editor
# 3. Find the TODO markers
# 4. Delete the implementation, keep the function signature
# 5. Write your own implementation
# 6. Run the test to check your work:
pnpm test:exercises ring-buffer     # TypeScript
cargo test ring_buffer     # Rust
go test -run RingBuffer    # Go
pytest ring_buffer/test_ring_buffer.py # Python

Separator line

// ─── Tests (do not modify below this line) ───────────────────────

Everything above this line is your playground. Everything below is the test suite.

What success / failure looks like

When your implementation is correct:

✓ Ring Buffer - Basic: should enqueue and dequeue in FIFO order (2ms)
✓ Ring Buffer - Basic: should reject enqueue when full

When something is wrong:

✗ Ring Buffer - Basic: should enqueue and dequeue in FIFO order
  → expected 1, got undefined

Answer Files

Reference implementations live in exercises/answers/<language>/<pattern>/:

exercises/answers/
├── typescript/   # 46 directories, one .ts each
├── rust/         # 46 directories, one .rs each
├── go/           # 46 directories, one .go each
└── python/       # 46 directories, one .py each

These contain pure implementation code (no tests). Use them to check your work or study alternative approaches.

Running All Languages at Once

# From the project root:
pnpm test:exercises                        # TypeScript (491 tests)
(cd exercises/rust && cargo test)          # Rust (173 tests)
(cd exercises/go && go test ./...)         # Go (176 tests)
(cd exercises/python && pytest)            # Python (233 tests)

Troubleshooting

Problem	Solution
nvm: command not found	Install nvm: curl -o- https://raw.githubusercontent.com/nvm-sh/nvm/v0.40.3/install.sh | bash
pnpm: command not found	Install pnpm: npm install -g pnpm
rustup: command not found	Install Rust: curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | sh
go: command not found	Download from go.dev/dl and add to PATH
pytest: command not found	pip install pytest (or pip3 install pytest)
TypeScript tests fail with import errors	Run pnpm install first
Rust tests fail to compile	Run rustup update to get latest stable
Go tests show module errors	Run go mod tidy in exercises/go/
Python ModuleNotFoundError	Each file is self-contained — no imports needed