vitest.config.ts

import { storybookTest } from '@storybook/addon-vitest/vitest-plugin';
import { playwright } from '@vitest/browser-playwright';
import { defineConfig } from 'vitest/config';
import { litCssPlugin } from './litcss';

// Storybook-driven tests: every story runs as a test in a real browser, with
// its `play` function as an interaction test and the a11y addon running axe.

// v8 coverage only instruments Chromium, so a --coverage run is Chromium-only;
// a plain `vitest` run adds Firefox and WebKit for cross-browser confidence.
// CI runs the coverage (Chromium) pass and a `--project=firefox --project=webkit`
// pass separately, so no engine runs twice. (Visual regression is a separate
// run — see vitest.visual.config.ts.)
const withCoverage = process.argv.includes('--coverage');

export default defineConfig({
  // litCssPlugin transforms component `*.css` imports; the Storybook build/dev
  // server picks it up from vite.config.ts, but this Vitest run doesn't load
  // that config, so it registers its own (see litcss.ts — once per pipeline).
  plugins: [litCssPlugin(), storybookTest({ configDir: '.storybook' })],
  // The run logs "Multiple versions of Lit loaded" — a known upstream Storybook
  // bug (storybookjs/storybook#31507), dev/test-only and harmless.
  test: {
    browser: {
      enabled: true,
      headless: true,
      provider: playwright(),
      instances: withCoverage
        ? [{ browser: 'chromium' }]
        : [
            { browser: 'chromium' },
            { browser: 'firefox' },
            { browser: 'webkit' },
          ],
    },
    coverage: {
      provider: 'v8',
      include: ['src/**'],
      exclude: [
        'src/generated/**',
        'src/**/*.stories.ts',
        'src/**/index.ts',
        'src/index.ts',
        'src/react/**',
      ],
      // A regression floor just under current coverage; ratchet up as the
      // suite grows. Keeping it close to actual is what catches slow erosion.
      thresholds: {
        statements: 94,
        lines: 96,
        functions: 95,
        branches: 78,
      },
    },
  },
});