@heilgar/pest-jest

Jest integration for pest (Prompt Evaluation & Scoring Toolkit) — add LLM prompt testing to your Jest test suite with custom expect() matchers.

Features

• Custom Jest matchers — expect(response).toContainToolCall(...), expect(response).toSatisfyCriteria(...), and more via expect.extend()
• LLM-as-judge — use a powerful model to score responses against plain-language criteria
• Deterministic + semantic assertions — verify tool calls, response schemas, text content, and semantic meaning
• Custom reporter — optional reporter for prompt test results
• TypeScript support — full type definitions for all matchers

Install

npm install @heilgar/pest-jest @heilgar/pest-core

Quick Start

// jest.config.ts
export default {
  setupFilesAfterFramework: ['@heilgar/pest-jest/setup'],
};

// tests/prompt.test.ts
import { send, createProvider } from '@heilgar/pest-core';
import { setJudge } from '@heilgar/pest-jest';

const provider = createProvider({ type: 'openai', model: 'gpt-4o', apiKey: '...' });
setJudge(provider);

test('responds helpfully', async () => {
  const res = await send(provider, 'Help me');
  await expect(res).toSatisfyCriteria('Response is helpful and friendly');
});

Documentation

Full docs at heilgar.github.io/pest

License

MIT