Regression in test-storybook after upgrading to 8.5.0: Axe is already running error

[akibarika]

Summary

After upgrading to Storybook 8.5.0, I encountered an issue when running yarn test-storybook in combination with axe-playwright. Specifically, the test runner throws the following error:

page.evaluate: Error: Axe is already running. Use `await axe.run()` to wait for the previous run to finish before starting a new run.

This issue occurs when running tests with --maxWorkers=2 or higher. However, it works fine if I downgrade back to 8.4.7 or if I reduce the number of workers to --maxWorkers=1 in 8.5.0.

Environment Details:

• Storybook Version: 8.5.0

• @storybook/test-runner Version: Latest (installed alongside Storybook 8.5.0)

• Test Runner Command:

yarn test-storybook --url http://127.0.0.1:6006/ --config-dir ./apps/storybook/.storybook --maxWorkers=2

• Temporary Solution: Changing --maxWorkers to 1 avoids the issue:

yarn test-storybook --url http://127.0.0.1:6006/ --config-dir ./apps/storybook/.storybook --maxWorkers=1

Questions:

• Was there a change in how @storybook/test-runner or Storybook 8.5.0 handles parallel worker processes?

• Is there a way to ensure compatibility with axe-playwright when running test-storybook with multiple workers?

• Are there any known workarounds or fixes to address this regression?

Additional information

• This issue does not occur when using the Storybook dev server (yarn storybook) instead of http-server. The same test works fine when pointed to http://localhost:4400 (the Storybook dev server) with --maxWorkers=2.

• I suspect this might be related to how lifecycle events are handled in @storybook/test-runner for static vs. dynamic Storybook builds in the 8.5.0 release.

• Similar issue [Investigation]: Support React 19 #29805 (comment)

Create a reproduction

//.storybook/test-runner.ts

import type { TestRunnerConfig } from '@storybook/test-runner';
import { getStoryContext } from '@storybook/test-runner';

import { injectAxe, checkA11y, configureAxe } from 'axe-playwright';

/*
 * See https://storybook.js.org/docs/writing-tests/test-runner#test-hook-api
 * to learn more about the test-runner hooks API.
 */
const config: TestRunnerConfig = {
  async preVisit(page) {
    await injectAxe(page);
  },
  async postVisit(page, context) {
    // Get the entire context of a story, including parameters, args, argTypes, etc.
    const storyContext = await getStoryContext(page, context);

    // Apply story-level a11y rules
    await configureAxe(page, {
      rules: storyContext.parameters?.a11y?.config?.rules,
    });

    const element = storyContext.parameters?.a11y?.element ?? 'body';
    await checkA11y(page, element, {
      detailedReport: true,
      detailedReportOptions: {
        html: true,
      },
    });
  },
};

export default config;