PDF Snapshot

Jest matcher for visual regression testing of PDF documents. Behaves just like Jest snapshots do.

Under the hood, it uses pdf.js for conversion of a pdf to png. In node, pdf.js depends on canvas. Finally, the comparison is happening via pixelmatch.

In order to be platform agnostic, the png conversion and png comparison is performed by a small server running aside, available as a Docker image and communicating with Jest matcher using tRCP.

Usage

Prerequisites

Before you begin, ensure you have met the following requirements:

• You have installed the latest version of Docker.

Installation

First pull the Docker image of the main service.

docker pull btravers/pdf-snapshot

Then install Jest matcher in the dev dependencies of your project.

npm install --save-dev @btravers/pdf-snapshot-jest

Please note that Jest 28 is a peerDependency.

Declare toMatchPdfSnapshot matcher in your Jest configuration.

"jest": {
  "setupFilesAfterEnv": [
    "@btravers/pdf-snapshot-jest/dist/toMatchPdfSnapshot"
  ]
}

If you are using Typescript add import('@btravers/pdf-snapshot-jest/dist/toMatchPdfSnapshot'); to your typings.

Invocation

Start the container with the main service.

docker run -d -p 3000:3000 btravers/pdf-snapshot

In your test, export PDF_SNAPSHOT_SERVER_URL environment variable in order to link Jest matcher with the service running in the container.

process.env.PDF_SNAPSHOT_SERVER_URL = 'http://localhost:3000'

Now, all you have to do in your tests is pass a pdf content as Buffer.

const pdfBuffer = await fs.promise.readFile('path to your pdf');
describe('test pdf report visual regression', () => {
  it('should match', () => expect(pdfBuffer).toMatchPdfSnapshot());
});

Go further

You can rely on testcontainers-node and automate the container start before tests run.

Credits

• pdf-visual-diff
• jest-image-snapshot