Get zero coverage with nyc and playwright

Question

I'm struggling to set up coverage correctly using Playwright. It reports 0 coverage in all files (except the test files themselves, if I include them).

I'm getting inspiration from https://playwright.dev/docs/api/class-coverage and https://github.com/bgotink/playwright-coverage/blob/main/src/fixtures.ts. Our project is a monorepo where tests in a folder e2e-tests/ run end to end tests on servers contained in other adjacent folders, e.g. frontend/.

The current setup is using a page fixture like so in each test-file:

// frontend.spec.ts
import { test, expect } from "../fixtures";

test("something", ({ page ) => {
    // Do test stuff with page
});

where the fixture is defined as

// fixtures/page.ts
import { Page, TestInfo } from "@playwright/test";

const pageWithCoverage = async (
  { page, browserName }: { page: Page; browserName: string },
  use: (page: Page) => Promise<void>,
  testInfo: TestInfo
) => {
  if (!page.coverage) throw new Error(`Could not collect coverage with browser "${browserName}"`);

  console.log("📈 Collecting coverage");
  await page.coverage.startJSCoverage();
  await use(page);
  await page.coverage.stopJSCoverage();
};

export default pageWithCoverage;

To collect coverage I run

npx nyc --all --cwd ".." --include "**/frontend/**/*  --nycrc-path e2e-tests/.nycrc npm t

where the relevant part concerning the file structure is:

 --all --cwd ".." --include "**/frontend/**/*"

I'm using a .nycrc file containing nyc-config-tsx in order to instrument tsx files:

// .nycrc
{
  "extends": "nyc-config-tsx",
  "all": true
}

Can you tell what the issue is?

The frontend is built using next.

I get similar results storing results to files using v8toIstanbul and running npx nyc report