Vitest and Jest matchers for Formfeed HTML templates kept in your repository. The offline matchers render with the same engine the API uses, so they need no account. Word and PowerPoint templates are tested with formfeed test, which compares their filled XML with approved snapshots.

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.