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Hoare is a fast, minimalist test runner for TypeScript and JavaScript, with a small, easy-to-learn API that lets you focus on your tests — not your tooling.

It emphasizes speed, clarity, safety, and minimal configuration.

Named after Sir Tony Hoare, the inventor of the Hoare Triple — a foundational idea in formal reasoning and software correctness.

🔒 Out-of-the-box Typescript support

• Written in Typescript. No special configuration needed, and no plugins to install.
• Works great with c8 for code coverage.
• Handles compilation errors gracefully.

🛡 Defensive

• Uncaught errors and unhandled promise rejections will cause the test to fail.
• Any spec files without tests, or tests without assertions, result in a failed test.
• Strict and deep equality comparison by default.

🚀 Fast & Reliable

• Multi-process parallel test runner. Each test file is run in its own process/runtime for performance and isolation benefits. Use on a multicore machine for best results.
• Optimized for speed and simplicity.
• Minimal dependencies.

😀 Easy to Use

• Very simple assertion API. No need to learn a new language/DSL or framework.
• Built-in powerful diff visualization tool and clean, organized output.
• Failed tests are easy to find, grouped at the end of the output.
• Errors or unhandled promise rejections are buffered and grouped under the test file in the output. This helps you know where they came from.
• Clean stack traces with no extra noise.

✨ Modern Features

• Async/Await/Promise Support
• Supports declarative and functional programming style
• Great with AI tools like Copilot, ChatGPT, and others.

Quick Examples

import {test} from 'hoare';

// Basic test

function greet(name: string): string {
  return `hello, ${name}`;
}

test('greet()', (assert) => {
  assert.equal(hello('world'), 'hello, world');
});

// Error handling

function throwError(): never {
  throw new Error('oops');
}

test('throwError()', (assert) => {
  assert.throws(() => throwError(), /oops/);
});

// Async test

async function fetchData(): Promise<string> {
  return Promise.resolve('data');
}

test('fetchData()', async (assert) => {
  const data = await fetchData();
  assert.equal(data, 'data');
});

Table of Contents

• Getting Started
• Examples
• API
• Visual Diff Tool
• Best Practices
• Inspiration, Philosophy & Attribution
• FAQ
• Support, Feedback, and Contributions
• Sponsorship
• License

Getting Started

To install and get started with hoare, see our Getting Started guide.

Examples

See the examples and src folders for more examples.

Support, feedback, and contributions

• Star this repo if you like it!
• Submit an issue with your problem, feature request or bug report
• Issue a PR against main and request review. Make sure all tests pass and coverage is good.
• Write about this project in your blog, tweet about it, or share it with your friends!

Sponsorship

Aeroview is a lightning-fast, developer-friendly, AI-powered logging IDE. Get started for free at https://aeroview.io.

Want to sponsor this project? Reach out.

Other useful libraries

• autorel: Automate semantic releases based on conventional commits. Similar to semantic-release but much simpler.
• brek: A powerful yet simple configuration library for Node.js. It’s structured, typed, and designed for dynamic configuration loading, making it perfect for securely managing secrets (e.g., AWS Secrets Manager).
• jsout: A Syslog-compatible, small, and simple logger for Typescript/Javascript projects.
• cjs-mock: NodeJS module mocking for CJS (CommonJS) modules for unit testing purposes.
• typura: Simple and extensible runtime input validation for TS/JS, written in TS.