test_runner: avoid reading process state directly in run()

doc/api/test.md

@@ -1546,6 +1546,9 @@ changes:
   * `setup` {Function} A function that accepts the `TestsStream` instance
     and can be used to setup listeners before any tests are run.
     **Default:** `undefined`.
+  * `env` {Object} Environment variables to pass to test child processes.
+    This option has no effect when `isolation` is `'none'`.
+    **Default:** `process.env`.
   * `execArgv` {Array} An array of CLI flags to pass to the `node` executable when
     spawning the subprocesses. This option has no effect when `isolation` is `'none`'.
     **Default:** `[]`

lib/internal/main/test_runner.js

@@ -30,7 +30,12 @@ if (isUsingInspector() && options.isolation === 'process') {
   options.inspectPort = process.debugPort;
 }
 
+// Capture process state explicitly so run() does not need to access it.
 options.globPatterns = ArrayPrototypeSlice(process.argv, 1);
+options.cwd = process.cwd();
+if (options.isolation !== 'none') {
+  options.env = process.env;
+}
 
 debug('test runner configuration:', options);
 run(options).on('test:summary', (data) => {

lib/internal/test_runner/runner.js

@@ -167,6 +167,7 @@ function getRunArgs(path, { forceExit,
                             only,
                             argv: suppliedArgs,
                             execArgv,
+                            globPatterns,
                             rerunFailuresFilePath,
                             root: { timeout },
                             cwd }) {
@@ -214,7 +215,9 @@ function getRunArgs(path, { forceExit,
 
   if (path === kIsolatedProcessName) {
     ArrayPrototypePush(runArgs, '--test');
-    ArrayPrototypePushApply(runArgs, ArrayPrototypeSlice(process.argv, 1));
+    if (globPatterns != null) {
+      ArrayPrototypePushApply(runArgs, globPatterns);
+    }
   } else {
     ArrayPrototypePush(runArgs, path);
   }
@@ -421,7 +424,7 @@ function runTestFile(path, filesWatcher, opts) {
   const subtest = opts.root.createSubtest(FileTest, testPath, testOpts, async (t) => {
     const args = getRunArgs(path, opts);
     const stdio = ['pipe', 'pipe', 'pipe'];
-    const env = { __proto__: null, NODE_TEST_CONTEXT: 'child-v8', ...(opts.env || process.env) };
+    const env = { __proto__: null, NODE_TEST_CONTEXT: 'child-v8', ...opts.env };
 
     // Acquire a worker ID from the pool for process isolation mode
     let workerId;
@@ -648,11 +651,22 @@ function run(options = kEmptyObject) {
     functionCoverage = 0,
     execArgv = [],
     argv = [],
-    cwd = process.cwd(),
+    cwd,
     rerunFailuresFilePath,
     env,
   } = options;
 
+  // Default to process state when not explicitly provided, maintaining
+  // backwards compatibility for public API users while allowing the
+  // internal CLI entry point to pass these values explicitly.
+  const userProvidedEnv = env !== undefined;
+  if (cwd === undefined) {
+    cwd = process.cwd();
+  }
+  if (env === undefined) {
+    env = process.env;
+  }
+
   if (files != null) {
     validateArray(files, 'options.files');
   }
@@ -759,7 +773,7 @@ function run(options = kEmptyObject) {
     validatePath(globalSetupPath, 'options.globalSetupPath');
   }
 
-  if (env != null) {
+  if (userProvidedEnv) {
     validateObject(env);
 
     if (isolation === 'none') {
@@ -836,7 +850,7 @@ function run(options = kEmptyObject) {
   };
 
   if (isolation === 'process') {
-    if (process.env.NODE_TEST_CONTEXT !== undefined) {
+    if (env.NODE_TEST_CONTEXT !== undefined) {
       process.emitWarning('node:test run() is being called recursively within a test file. skipping running files.');
       root.postRun();
       return root.reporter;

test/parallel/test-runner-run.mjs

@@ -687,6 +687,27 @@ describe('forceExit', () => {
       message: /The property 'options\.forceExit' is not supported with watch mode\./
     });
   });
+
+  it('should accept env option and pass it to child processes', async () => {
+    const stream = run({
+      files: [join(testFixtures, 'default-behavior/test/random.cjs')],
+      env: { ...process.env, NODE_TEST_CUSTOM_ENV_VAR: '1' },
+    });
+    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);
+  });
+
+  it('should reject env option with isolation none', () => {
+    assert.throws(() => run({
+      files: [join(testFixtures, 'default-behavior/test/random.cjs')],
+      isolation: 'none',
+      env: { FOO: 'bar' },
+    }), {
+      code: 'ERR_INVALID_ARG_VALUE',
+    });
+  });
 });