test_runner: fix watch cwd with isolation none

When watch mode runs with isolation disabled, spawn the child test
runner with the files or glob patterns from the current run instead
of reusing the parent process argv.

This keeps discovery scoped to the configured cwd and avoids rerunning
the driver test when the parent argv points outside that cwd.

Fixes: #63689

Signed-off-by: Kamat, Trivikram <16024985+trivikr@users.noreply.github.com>
Assisted-by: openai:gpt-5.5
PR-URL: #63690
Fixes: #63689
Refs: https://github.com/nodejs/reliability/blob/main/reports/2026-06-01.md#jstest-failure
Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
Reviewed-By: Chemi Atlow <chemi@atlow.co.il>

Author: trivikr

lib/internal/test_runner/runner.js

@@ -12,7 +12,6 @@ const {
   ArrayPrototypePush,
   ArrayPrototypePushApply,
   ArrayPrototypeShift,
-  ArrayPrototypeSlice,
   ArrayPrototypeSome,
   ArrayPrototypeSort,
   MathMax,
@@ -175,6 +174,9 @@ function getRunArgs(path, { forceExit,
                             testNamePatterns,
                             testSkipPatterns,
                             only,
+                            hasFiles,
+                            testFiles,
+                            globPatterns,
                             argv: suppliedArgs,
                             execArgv,
                             rerunFailuresFilePath,
@@ -232,7 +234,8 @@ function getRunArgs(path, { forceExit,
 
   if (path === kIsolatedProcessName) {
     ArrayPrototypePush(runArgs, '--test');
-    ArrayPrototypePushApply(runArgs, ArrayPrototypeSlice(process.argv, 1));
+    ArrayPrototypePush(runArgs, '--test-isolation=none');
+    ArrayPrototypePushApply(runArgs, hasFiles ? testFiles : globPatterns ?? []);
   } else {
     ArrayPrototypePush(runArgs, path);
   }
@@ -951,6 +954,7 @@ function run(options = kEmptyObject) {
     workerIdPool: isolation === 'process' ? workerIdPool : null,
     randomize,
     randomSeed,
+    testFiles,
   };
 
   if (isolation === 'process') {

test/test-runner/test-run-watch-cwd-isolation-none-argv.mjs

@@ -0,0 +1,43 @@
+// Test run({ watch: true, cwd, isolation: 'none' }) does not reuse the
+// parent process argv when spawning the watch child.
+import * as common from '../common/index.mjs';
+import assert from 'node:assert';
+import { readFileSync, writeFileSync } from 'node:fs';
+import { join } from 'node:path';
+import { run } from 'node:test';
+import tmpdir from '../common/tmpdir.js';
+import { skipIfNoWatch } from '../common/watch.js';
+
+skipIfNoWatch();
+tmpdir.refresh();
+
+const marker = join(tmpdir.path, 'marker');
+writeFileSync(join(tmpdir.path, 'test.js'), `
+const test = require('node:test');
+const { writeFileSync } = require('node:fs');
+
+test('test ran from cwd', () => {
+  writeFileSync(${JSON.stringify(marker)}, 'ran');
+});
+`);
+
+const controller = new AbortController();
+const stream = run({
+  cwd: tmpdir.path,
+  watch: true,
+  signal: controller.signal,
+  isolation: 'none',
+}).on('data', function({ type }) {
+  if (type === 'test:watch:drained') {
+    stream.removeAllListeners('test:fail');
+    stream.removeAllListeners('test:pass');
+    controller.abort();
+  }
+});
+
+stream.on('test:fail', common.mustNotCall());
+stream.on('test:pass', common.mustCall(1));
+// eslint-disable-next-line no-unused-vars
+for await (const _ of stream);
+
+assert.strictEqual(readFileSync(marker, 'utf8'), 'ran');