Firecrawl local dev loop

Firecrawl Local Dev Loop

Overview

Set up a fast development workflow for Firecrawl integrations. Use self-hosted Firecrawl via Docker to avoid burning API credits during development, mock the SDK for unit tests, and run integration tests against the local instance.

Prerequisites

• Node.js 18+ with npm/pnpm
• Docker + Docker Compose (for self-hosted Firecrawl)
• @mendable/firecrawl-js installed

Instructions

Step 1: Project Structure

my-firecrawl-project/
├── src/
│   ├── scraper.ts          # Firecrawl business logic
│   └── config.ts           # Environment-aware config
├── tests/
│   ├── scraper.test.ts     # Unit tests (mocked SDK)
│   └── integration.test.ts # Integration tests (real API)
├── docker-compose.yml      # Self-hosted Firecrawl
├── .env.local              # Dev secrets (git-ignored)
├── .env.example            # Template for team
└── package.json

Step 2: Self-Hosted Firecrawl for Zero-Credit Dev

# docker-compose.yml
services:
  firecrawl:
    image: mendableai/firecrawl:latest
    ports:
      - "3002:3002"
    environment:
      - PORT=3002
      - USE_DB_AUTHENTICATION=false
      - REDIS_URL=redis://redis:6379
      - NUM_WORKERS_PER_QUEUE=1
      - BULL_AUTH_KEY=devonly
    depends_on:
      redis:
        condition: service_healthy

  redis:
    image: redis:7-alpine
    ports:
      - "6379:6379"
    healthcheck:
      test: ["CMD", "redis-cli", "ping"]
      interval: 5s
      timeout: 3s
      retries: 5

set -euo pipefail
# Start local Firecrawl
docker compose up -d

# Verify it's running
curl -s http://localhost:3002/health | jq .

Step 3: Environment-Aware Configuration

// src/config.ts
import FirecrawlApp from "@mendable/firecrawl-js";

export function getFirecrawl(): FirecrawlApp {
  const isDev = process.env.NODE_ENV !== "production";

  return new FirecrawlApp({
    apiKey: process.env.FIRECRAWL_API_KEY || "fc-dev",
    // Point to local Docker instance in dev
    ...(isDev && process.env.FIRECRAWL_API_URL
      ? { apiUrl: process.env.FIRECRAWL_API_URL }
      : {}),
  });
}

# .env.local (for development — zero API credits used)
FIRECRAWL_API_KEY=fc-localdev
FIRECRAWL_API_URL=http://localhost:3002
NODE_ENV=development

Step 4: Unit Tests with Mocked SDK

// tests/scraper.test.ts
import { describe, it, expect, vi, beforeEach } from "vitest";

// Mock the SDK
vi.mock("@mendable/firecrawl-js", () => ({
  default: vi.fn().mockImplementation(() => ({
    scrapeUrl: vi.fn().mockResolvedValue({
      success: true,
      markdown: "# Hello World\n\nSample content from mock",
      metadata: { title: "Hello World", sourceURL: "https://example.com" },
    }),
    crawlUrl: vi.fn().mockResolvedValue({
      success: true,
      data: [
        {
          markdown: "# Page 1",
          metadata: { sourceURL: "https://example.com/page1" },
        },
      ],
    }),
    mapUrl: vi.fn().mockResolvedValue({
      success: true,
      links: ["https://example.com/a", "https://example.com/b"],
    }),
  })),
}));

import { scrapeAndProcess } from "../src/scraper";

describe("Scraper", () => {
  it("returns cleaned markdown", async () => {
    const result = await scrapeAndProcess("https://example.com");
    expect(result.markdown).toContain("Hello World");
    expect(result.metadata.title).toBe("Hello World");
  });
});

Step 5: Integration Tests Against Local Instance

// tests/integration.test.ts
import { describe, it, expect } from "vitest";
import FirecrawlApp from "@mendable/firecrawl-js";

const FIRECRAWL_URL = process.env.FIRECRAWL_API_URL || "http://localhost:3002";

describe.skipIf(!process.env.FIRECRAWL_API_URL)("Firecrawl Integration", () => {
  const firecrawl = new FirecrawlApp({
    apiKey: "fc-test",
    apiUrl: FIRECRAWL_URL,
  });

  it("scrapes a page to markdown", async () => {
    const result = await firecrawl.scrapeUrl("https://example.com", {
      formats: ["markdown"],
    });
    expect(result.success).toBe(true);
    expect(result.markdown).toBeDefined();
    expect(result.markdown!.length).toBeGreaterThan(50);
  }, 30000);
});

Step 6: Dev Scripts

{
  "scripts": {
    "dev": "tsx watch src/index.ts",
    "test": "vitest",
    "test:watch": "vitest --watch",
    "test:integration": "FIRECRAWL_API_URL=http://localhost:3002 vitest run tests/integration",
    "firecrawl:up": "docker compose up -d",
    "firecrawl:down": "docker compose down",
    "firecrawl:logs": "docker compose logs -f firecrawl"
  }
}

Output

• Self-hosted Firecrawl running on localhost:3002
• Unit tests with mocked SDK (zero API calls)
• Integration tests against local instance
• Hot-reload dev server with tsx watch

Error Handling

Error	Cause	Solution
Docker ECONNREFUSED	Container not running	docker compose up -d
Redis connection refused	Redis not healthy yet	Wait for healthcheck, retry
MODULE_NOT_FOUND	Missing dependency	npm install @mendable/firecrawl-js
Integration test timeout	Self-hosted Firecrawl slow	Increase vitest timeout to 30s
Port 3002 in use	Another process	lsof -i :3002 and kill, or change port

Examples

Quick Scrape Script for Dev

// scripts/dev-scrape.ts
import { getFirecrawl } from "../src/config";

const firecrawl = getFirecrawl();
const result = await firecrawl.scrapeUrl(process.argv[2] || "https://example.com", {
  formats: ["markdown"],
});
console.log(result.markdown);

npx tsx scripts/dev-scrape.ts https://docs.firecrawl.dev

Resources

• Firecrawl Self-Hosting
• Vitest Documentation
• tsx (TypeScript Execute)

Next Steps

See firecrawl-sdk-patterns for production-ready code patterns.