fix(browser): fix updating snapshot during watch mode (#4867)

Co-authored-by: Vladimir <sleuths.slews0s@icloud.com>

Author: hi-ogawa

test/browser/fixtures/update-snapshot/__snapshots__/basic.test.ts.snap

@@ -0,0 +1,3 @@
+// Vitest Snapshot v1, https://vitest.dev/guide/snapshot.html
+
+exports[`basic 1`] = `1`;

test/browser/fixtures/update-snapshot/basic.test.ts

@@ -0,0 +1,5 @@
+import { expect, test } from 'vitest'
+
+test('basic', () => {
+  expect(1).toMatchSnapshot()
+})

test/browser/fixtures/update-snapshot/vitest.config.ts

@@ -0,0 +1,26 @@
+import path from 'node:path'
+import { fileURLToPath } from 'node:url'
+import { defineConfig } from 'vitest/config'
+
+/*
+manually test snapshot by
+  pnpm -C test/browser test-fixtures --root fixtures/update-snapshot
+*/
+
+const provider = process.env.PROVIDER || 'webdriverio'
+const browser =
+  process.env.BROWSER || (provider === 'playwright' ? 'chromium' : 'chrome')
+
+export default defineConfig({
+  test: {
+    browser: {
+      enabled: true,
+      provider,
+      name: browser,
+    },
+  },
+  cacheDir: path.join(
+    path.dirname(fileURLToPath(import.meta.url)),
+    'node_modules/.vite'
+  ),
+})

test/browser/package.json

@@ -7,6 +7,7 @@
     "test:webdriverio": "PROVIDER=webdriverio node --test --test-concurrency=1 specs/",
     "test:playwright": "PROVIDER=playwright node --test --test-concurrency=1 specs/",
     "test:safaridriver": "PROVIDER=webdriverio BROWSER=safari node --test --test-concurrency=1 specs/",
+    "test-fixtures": "vitest",
     "coverage": "vitest --coverage.enabled --coverage.provider=istanbul --browser.headless=yes"
   },
   "devDependencies": {

test/browser/specs/update-snapshot.test.mjs

@@ -0,0 +1,70 @@
+import assert from 'node:assert'
+import fs from 'node:fs'
+import test from 'node:test'
+import { startVitest } from 'vitest/node'
+
+let vitest
+
+test.after(async () => {
+  await vitest?.close()
+})
+
+test('update snapshot', async () => {
+  // setup wrong snapshot value
+  const snapshotPath = './fixtures/update-snapshot/__snapshots__/basic.test.ts.snap'
+  await editFile(snapshotPath, data => data.replace('`1`', '`2`'))
+
+  // run vitest watch mode
+  const result = await wrapExit(() => startVitest('test', [], {
+    watch: true,
+    root: './fixtures/update-snapshot',
+    reporters: ['tap-flat'], // use simple reporter to not pollute stdout
+    browser: { headless: true },
+  }))
+  vitest = result.value
+  assert.ok(vitest)
+
+  // test fails
+  assert.equal(result.exitCode, 1)
+  assert.equal(vitest.state.getFiles()[0].result.state, 'fail')
+
+  // updateSnapshot API to simulate "u" commmand
+  await vitest.updateSnapshot()
+
+  // verify snapshot value is updated
+  const snapshotData = await fs.promises.readFile(snapshotPath, 'utf-8')
+  assert.match(snapshotData, /`1`/)
+
+  // test passes
+  assert.equal(vitest.state.getFiles()[0].result.state, 'pass')
+})
+
+/**
+ * @param {string} filepath
+ * @param {(data: string) => string} edit
+ */
+async function editFile(filepath, edit) {
+  const data = await fs.promises.readFile(filepath, 'utf-8')
+  await fs.promises.writeFile(filepath, edit(data))
+}
+
+/**
+ * run function and return mutated exitCode while preserving current exitCode
+ * @param {() => any} f
+ */
+async function wrapExit(f) {
+  const prevExitCode = process.exitCode
+  const prevExit = process.exit
+  process.exit = () => {}
+  /** @type {{ value?: any, exitCode?: number }} */
+  const result = {}
+  try {
+    result.value = await f()
+  }
+  finally {
+    result.exitCode = process.exitCode
+    process.exitCode = prevExitCode
+    process.exit = prevExit
+  }
+  return result
+}