Breakcheck Core

This package provides the core programmatic API for Breakcheck. Use this library to integrate website snapshotting, comparison, and viewing directly into your own JavaScript or TypeScript projects.

This package is intended for developers who need to build custom automation or tooling. If you're looking to use Breakcheck from the command line, see the main breakcheck package.

Installation

npm install breakcheck-core

API Usage

The breakcheck-core library exposes a set of simple, asynchronous functions to manage the entire workflow.

Creating a Snapshot

To begin, you need to create a "snapshot" of a website. A snapshot is a record of a site's state at a specific point in time, created by crawling the site and saving its content.

The createSnapshotFromConfig function takes a configuration object and returns the results of the crawl.

import { createSnapshotFromConfig } from "breakcheck-core";

async function takeSnapshot() {
  const snapshotConfig = {
    // The URL where the crawler will start
    baseUrl: "http://localhost:3000",

    // A unique name for this snapshot
    name: "my-site-before-changes",

    // Settings for the crawler
    crawlSettings: {
      baseUrl: "http://localhost:3000",
      // 'cheerio' for static sites, 'playwright' for dynamic, JS-heavy sites
      crawlerType: "cheerio",
      maxDepth: 3, // How many links deep to follow
    },

    // Optional: Write a list of all crawled URLs to a file
    urlListPath: "./crawled-urls.txt",
  };

  const result = await createSnapshotFromConfig(snapshotConfig);

  if (result.status === "success") {
    console.log(`✅ Snapshot created: ${result.snapshotId}`);
    console.log(`📊 Pages crawled: ${result.pageCount}`);
  } else {
    console.error(`❌ Snapshot failed: ${result.message}`);
  }
}

takeSnapshot();

Listing Snapshots

You can get a list of all locally saved snapshots using the listSnapshots function.

import { listSnapshots } from "breakcheck-core";

async function showSnapshots() {
  const snapshots = await listSnapshots();

  if (snapshots.length === 0) {
    console.log("No snapshots found.");
    return;
  }

  console.log("Available Snapshots:");
  snapshots.forEach((snapshot) => {
    console.log(
      `- ${snapshot.name} (${snapshot.pageCount} pages, created on ${snapshot.date})`
    );
  });
}

showSnapshots();

Running a Comparison

The core of the tool is comparing two snapshots. The runComparison function compares a "before" and "after" snapshot, applies rules to ignore dynamic content, and saves a detailed diff report.

import { runComparison } from "breakcheck-core";

async function compareStates() {
  const comparisonConfig = {
    // The name of the 'before' snapshot
    beforeSnapshotId: "my-site-before-changes",

    // The name of the 'after' snapshot
    afterSnapshotId: "my-site-after-changes",

    // A unique name for the comparison results directory
    comparisonName: "v1-vs-v2-comparison",

    // The ruleset to apply. 'default' uses built-in baseline rules.
    // You can also provide a path to a rules file or a ruleset object.
    ruleset: "default",
  };

  const summary = await runComparison(comparisonConfig);

  if (summary.status === "completed") {
    console.log(`✅ Comparison complete!`);
    console.log(`   - Overall result: ${summary.overallResult.toUpperCase()}`);
    console.log(`   - Pages with differences: ${summary.pagesWithDifferences}`);
    console.log(`   - Results saved to: ${summary.resultsPath}`);
  } else {
    console.error("❌ Comparison failed.");
  }
}

compareStates();

Viewing Comparison Results

After a comparison is complete, you can launch a local web server to view the results in your browser. The startViewServer function starts an Express server that renders the diffs.

import { startViewServer } from "breakcheck-core";

async function viewResults() {
  const comparisonName = "v1-vs-v2-comparison"; // The name of the comparison to view
  const port = 8080;

  try {
    const server = await startViewServer(comparisonName, port);
    console.log(`🌐 View server running at http://localhost:${port}`);
    console.log("Press Ctrl+C to stop the server.");

    // You can add logic to automatically open the browser or close the server
    // For example, to stop it after 60 seconds:
    // setTimeout(() => server.close(), 60000);
  } catch (error) {
    console.error(`❌ Could not start view server: ${error.message}`);
  }
}

viewResults();