Vitest and Jest matchers for Formfeed templates kept in your repository. The offline matchers render with the same engine the API uses, so they need no account.

npm install -D @formfeed/testing

Register the matchers once: add @formfeed/testing/vitest to Vitest's setupFiles, or @formfeed/testing/jest to Jest's setupFilesAfterEnv.

import { loadTemplate } from '@formfeed/testing';
import invoice from '../templates/invoice-de/data/default.json';

const tpl = await loadTemplate('templates/invoice-de');

test('compiles and uses only known variables', async () => {
  await expect(tpl).toRenderWithoutErrors(invoice);
  await expect(tpl).toUseOnlyKnownVariables(invoice);
});

test('html snapshot', async () => {
  expect(await tpl.render(invoice)).toMatchSnapshot();
});

test('two pages for forty lines', async () => {
  await expect(tpl).toHavePageCount(2, invoice); // a true render through the API
});

Matcher	Needs the API	Checks
`toRenderWithoutErrors(data)`	no	Compiles and renders without engine errors
`toUseOnlyKnownVariables(data)`	no	Every variable the template reads exists in the data
`toContainText(text, data)`	no	The rendered HTML contains the text
`toHavePageCount(n, data)`	yes	Page count of the true render

API-backed matchers read FORMFEED_API_KEY (a test key is enough) and skip with a warning without one; set FORMFEED_REQUIRE_API=1 in CI to make them fail instead. For another test runner, pass matchers to its expect.extend.