test: add postcss custom feature test case

test/e2e/basic.browser.test.js

@@ -40,7 +40,13 @@ describe('basic browser', () => {
     await page.nuxt.navigate('/css')
 
     expect(await page.$text('.red')).toBe('This is red')
-    expect(await page.$eval('.red', red => window.getComputedStyle(red).color)).toBe('rgb(255, 0, 0)')
+    expect(await page.$eval('.red', red => {
+      const { color, backgroundColor } = window.getComputedStyle(red)
+      return { color, backgroundColor }
+    })).toEqual({
+      color: 'rgb(255, 0, 0)',
+      backgroundColor: 'rgb(0, 0, 255)'
+    })
   })
 
   test.skip('/stateful', async () => {

test/fixtures/basic/nuxt.config.js

@@ -36,7 +36,11 @@ export default {
   build: {
     scopeHoisting: true,
     postcss: [
-      require('postcss-preset-env')()
+      require('postcss-preset-env')({
+        features: {
+          'custom-selectors': true
+        }
+      })
     ]
   }
 }