fix: remove browser.fileParallelism (#5790)

Author: sheremet-va

Diff for: docs/config/index.md

@@ -1536,20 +1536,6 @@ Run the browser in a `headless` mode. If you are running Vitest in CI, it will b
 
 Run every test in a separate iframe.
 
-### browser.fileParallelism {#browser-fileparallelism}
-
-- **Type:** `boolean`
-- **Default:** the same as [`fileParallelism`](#fileparallelism)
-- **CLI:** `--browser.fileParallelism=false`
-
-Create all test iframes at the same time so they are running in parallel.
-
-This makes it impossible to use interactive APIs (like clicking or hovering) because there are several iframes on the screen at the same time, but if your tests don't rely on those APIs, it might be much faster to just run all of them at the same time.
-
-::: tip
-If you disabled isolation via [`browser.isolate=false`](#browser-isolate), your test files will still run one after another because of the nature of the test runner.
-:::
-
 #### browser.api
 
 - **Type:** `number | { port?, strictPort?, host? }`

Diff for: docs/guide/cli-table.md

@@ -57,7 +57,6 @@
 | `--browser.providerOptions <options>` | Options that are passed down to a browser provider. Visit [`browser.providerOptions`](https://vitest.dev/config/#browser-provideroptions) for more information |
 | `--browser.slowHijackESM` | Let Vitest use its own module resolution on the browser to enable APIs such as vi.mock and vi.spyOn. Visit [`browser.slowHijackESM`](https://vitest.dev/config/#browser-slowhijackesm) for more information (default: `false`) |
 | `--browser.isolate` | Run every browser test file in isolation. To disable isolation, use `--browser.isolate=false` (default: `true`) |
-| `--browser.fileParallelism` | Should all test files run in parallel. Use `--browser.file-parallelism=false` to disable (default: same as `--file-parallelism`) |
 | `--pool <pool>` | Specify pool, if not running in the browser (default: `threads`) |
 | `--poolOptions.threads.isolate` | Isolate tests in threads pool (default: `true`) |
 | `--poolOptions.threads.singleThread` | Run tests inside a single thread (default: `false`) |

Diff for: packages/browser/src/client/main.ts

@@ -100,42 +100,29 @@ client.ws.addEventListener('open', async () => {
     }
   })
 
-  const fileParallelism = config.browser.fileParallelism ?? config.fileParallelism
-
   if (config.isolate === false) {
     createIframe(
       container,
       ID_ALL,
     )
   }
   else {
-    // if fileParallelism is enabled, we can create all iframes at once
-    if (fileParallelism) {
-      for (const file of testFiles) {
-        createIframe(
-          container,
-          file,
-        )
-      }
-    }
-    else {
-      // otherwise, we need to wait for each iframe to finish before creating the next one
-      // this is the most stable way to run tests in the browser
-      for (const file of testFiles) {
-        createIframe(
-          container,
-          file,
-        )
-        await new Promise<void>((resolve) => {
-          channel.addEventListener('message', function handler(e: MessageEvent<IframeChannelEvent>) {
-            // done and error can only be triggered by the previous iframe
-            if (e.data.type === 'done' || e.data.type === 'error') {
-              channel.removeEventListener('message', handler)
-              resolve()
-            }
-          })
+    // otherwise, we need to wait for each iframe to finish before creating the next one
+    // this is the most stable way to run tests in the browser
+    for (const file of testFiles) {
+      createIframe(
+        container,
+        file,
+      )
+      await new Promise<void>((resolve) => {
+        channel.addEventListener('message', function handler(e: MessageEvent<IframeChannelEvent>) {
+          // done and error can only be triggered by the previous iframe
+          if (e.data.type === 'done' || e.data.type === 'error') {
+            channel.removeEventListener('message', handler)
+            resolve()
+          }
         })
-      }
+      })
     }
   }
 })

Diff for: packages/vitest/src/node/cli/cli-config.ts

@@ -350,9 +350,6 @@ export const cliOptionsConfig: VitestCLIOptions = {
       ui: {
         description: 'Show Vitest UI when running tests',
       },
-      fileParallelism: {
-        description: 'Should all test files run in parallel. Use `--browser.file-parallelism=false` to disable (default: same as `--file-parallelism`)',
-      },
       indexScripts: null,
       testerScripts: null,
       commands: null,

Diff for: packages/vitest/src/node/config.ts

@@ -149,7 +149,6 @@ export function resolveConfig(
     resolved.minWorkers = Number(resolved.minWorkers)
 
   resolved.browser ??= {} as any
-  resolved.browser.fileParallelism ??= resolved.fileParallelism ?? false
 
   // run benchmark sequentially by default
   resolved.fileParallelism ??= mode !== 'benchmark'

Diff for: packages/vitest/src/types/browser.ts

@@ -94,13 +94,6 @@ export interface BrowserConfigOptions {
    */
   ui?: boolean
 
-  /**
-   * Run test files in parallel. Fallbacks to `test.fileParallelism`.
-   *
-   * @default test.fileParallelism
-   */
-  fileParallelism?: boolean
-
   /**
    * Scripts injected into the tester iframe.
    */

Diff for: test/browser/specs/runner.test.ts

@@ -1,10 +1,7 @@
 import { beforeAll, describe, expect, onTestFailed, test } from 'vitest'
 import { runBrowserTests } from './utils'
 
-describe.each([
-  ['non parallel', false],
-  ['parallel', true],
-])('[%s] running browser tests', async (description, fileParallelism) => {
+describe('running browser tests', async () => {
   let stderr: string
   let stdout: string
   let browserResultJson: any
@@ -18,14 +15,10 @@ describe.each([
       browserResultJson,
       passedTests,
       failedTests,
-    } = await runBrowserTests({
-      browser: {
-        fileParallelism,
-      },
-    }))
+    } = await runBrowserTests())
   })
 
-  test(`[${description}] tests are actually running`, () => {
+  test('tests are actually running', () => {
     onTestFailed(() => {
       console.error(stderr)
     })
@@ -38,14 +31,14 @@ describe.each([
     expect(stderr).not.toContain('Unhandled Error')
   })
 
-  test(`[${description}] correctly prints error`, () => {
+  test('correctly prints error', () => {
     expect(stderr).toContain('expected 1 to be 2')
     expect(stderr).toMatch(/- 2\s+\+ 1/)
     expect(stderr).toContain('Expected to be')
     expect(stderr).toContain('But got')
   })
 
-  test(`[${description}] logs are redirected to stdout`, () => {
+  test('logs are redirected to stdout', () => {
     expect(stdout).toContain('stdout | test/logs.test.ts > logging to stdout')
     expect(stdout).toContain('hello from console.log')
     expect(stdout).toContain('hello from console.info')
@@ -65,26 +58,26 @@ describe.each([
     expect(stdout).toMatch(/time: [\d.]+ ms/)
   })
 
-  test(`[${description}] logs are redirected to stderr`, () => {
+  test('logs are redirected to stderr', () => {
     expect(stderr).toContain('stderr | test/logs.test.ts > logging to stderr')
     expect(stderr).toContain('hello from console.error')
     expect(stderr).toContain('hello from console.warn')
     expect(stderr).toContain('Timer "invalid timeLog" does not exist')
     expect(stderr).toContain('Timer "invalid timeEnd" does not exist')
   })
 
-  test(`[${description}] stack trace points to correct file in every browser`, () => {
-    // dependeing on the browser it references either `.toBe()` or `expect()`
+  test('stack trace points to correct file in every browser', () => {
+    // dependeing on the browser it references either '.toBe()' or 'expect()'
     expect(stderr).toMatch(/test\/failing.test.ts:4:(12|17)/)
   })
 
-  test(`[${description}] popup apis should log a warning`, () => {
+  test('popup apis should log a warning', () => {
     expect(stderr).toContain('Vitest encountered a `alert("test")`')
     expect(stderr).toContain('Vitest encountered a `confirm("test")`')
     expect(stderr).toContain('Vitest encountered a `prompt("test")`')
   })
 
-  test(`[${description}] snapshot inaccessible file debuggability`, () => {
+  test('snapshot inaccessible file debuggability', () => {
     expect(stderr).toContain('Access denied to "/inaccesible/path".')
   })
 })