feat: add spawnTest harness global

eslint.config.js

@@ -9,7 +9,7 @@ export default defineConfig([
   tseslint.configs.recommended,
   {
     files: [
-      "tests/**/*.js",
+      "tests/**/*.{mjs,js}",
     ],
     languageOptions: {
       // Only allow ECMAScript built-ins and CTS harness globals.
@@ -22,6 +22,7 @@ export default defineConfig([
         mustCall: "readonly",
         mustNotCall: "readonly",
         gcUntil: "readonly",
+        spawnTest: "readonly",
         experimentalFeatures: "readonly",
         napiVersion: "readonly",
         skipTest: "readonly",

implementors/node/child_process.d.ts

@@ -0,0 +1,16 @@
+export interface SpawnTestOptions {
+  cwd?: string;
+  nodeFlags?: string[];
+}
+
+export interface SpawnTestResult {
+  status: number | null;
+  signal: NodeJS.Signals | null;
+  stdout: string;
+  stderr: string;
+}
+
+export function spawnTest(
+  filePath: string,
+  options?: SpawnTestOptions
+): SpawnTestResult;

implementors/node/child_process.js

@@ -0,0 +1,49 @@
+import { spawnSync } from "node:child_process";
+import path from "node:path";
+
+const HARNESS_MODULE_PATHS = [
+  "features.js",
+  "assert.js",
+  "load-addon.js",
+  "gc.js",
+  "must-call.js",
+  "child_process.js",
+].map((file) => path.join(import.meta.dirname, file));
+
+/**
+ * Runs a test file in a fresh Node.js subprocess with the CTS harness globals
+ * pre-loaded, and returns its exit status, signal, and captured output.
+ *
+ * @param {string} filePath - Path to the JS/MJS file to execute. Resolved
+ *   against `options.cwd` if relative.
+ * @param {{ cwd?: string, nodeFlags?: string[] }} [options]
+ *   - `cwd`: working directory for the child; defaults to `process.cwd()`.
+ *   - `nodeFlags`: CLI flags passed to `node` before the `--import` chain
+ *     (e.g., `["--expose-gc"]`). Defaults to no flags so each caller declares
+ *     what its child needs.
+ * @returns {{ status: number | null, signal: NodeJS.Signals | null, stdout: string, stderr: string }}
+ */
+export const spawnTest = (filePath, options = {}) => {
+  const args = [...(options.nodeFlags ?? [])];
+  for (const modulePath of HARNESS_MODULE_PATHS) {
+    args.push("--import", "file://" + modulePath);
+  }
+  args.push(filePath);
+
+  const result = spawnSync(process.execPath, args, {
+    cwd: options.cwd ?? process.cwd(),
+    maxBuffer: 100 * 1024 * 1024,
+  });
+  if (result.error) throw result.error;
+  return {
+    status: result.status,
+    signal: result.signal,
+    stderr: result.stderr?.toString() ?? "",
+    stdout: result.stdout?.toString() ?? "",
+  };
+};
+
+// This module is loaded in both contexts: imported by the parent test runner
+// (tests.ts) and `--import`ed into every spawned child. The side effect below
+// installs `spawnTest` on the child's globalThis so tests can call it directly.
+Object.assign(globalThis, { spawnTest });

implementors/node/tests.ts

@@ -1,45 +1,16 @@
 import assert from "node:assert";
-import { spawn } from "node:child_process";
 import fs from "node:fs";
 import path from "node:path";
 
+import { spawnTest } from "./child_process.js";
+
 assert(
   typeof import.meta.dirname === "string",
   "Expecting a recent Node.js runtime API version"
 );
 
 const ROOT_PATH = path.resolve(import.meta.dirname, "..", "..");
 const TESTS_ROOT_PATH = path.join(ROOT_PATH, "tests");
-const FEATURES_MODULE_PATH = path.join(
-  ROOT_PATH,
-  "implementors",
-  "node",
-  "features.js"
-);
-const ASSERT_MODULE_PATH = path.join(
-  ROOT_PATH,
-  "implementors",
-  "node",
-  "assert.js"
-);
-const LOAD_ADDON_MODULE_PATH = path.join(
-  ROOT_PATH,
-  "implementors",
-  "node",
-  "load-addon.js"
-);
-const GC_MODULE_PATH = path.join(
-  ROOT_PATH,
-  "implementors",
-  "node",
-  "gc.js"
-);
-const MUST_CALL_MODULE_PATH = path.join(
-  ROOT_PATH,
-  "implementors",
-  "node",
-  "must-call.js"
-);
 
 export function listDirectoryEntries(dir: string) {
   const entries = fs.readdirSync(dir, { withFileTypes: true });
@@ -60,61 +31,26 @@ export function listDirectoryEntries(dir: string) {
   return { directories, files };
 }
 
-export function runFileInSubprocess(
-  cwd: string,
-  filePath: string
-): Promise<void> {
-  return new Promise((resolve, reject) => {
-    const child = spawn(
-      process.execPath,
-      [
-        // Using file scheme prefix when to enable imports on Windows
-        "--expose-gc",
-        "--import",
-        "file://" + FEATURES_MODULE_PATH,
-        "--import",
-        "file://" + ASSERT_MODULE_PATH,
-        "--import",
-        "file://" + LOAD_ADDON_MODULE_PATH,
-        "--import",
-        "file://" + GC_MODULE_PATH,
-        "--import",
-        "file://" + MUST_CALL_MODULE_PATH,
-        filePath,
-      ],
-      { cwd }
-    );
-
-    let stderrOutput = "";
-    child.stderr.setEncoding("utf8");
-    child.stderr.on("data", (chunk) => {
-      stderrOutput += chunk;
-    });
-
-    child.stdout.pipe(process.stdout);
-
-    child.on("error", reject);
-
-    child.on("close", (code, signal) => {
-      if (code === 0) {
-        resolve();
-        return;
-      }
-
-      const reason =
-        code !== null ? `exit code ${code}` : `signal ${signal ?? "unknown"}`;
-      const trimmedStderr = stderrOutput.trim();
-      const stderrSuffix = trimmedStderr
-        ? `\n--- stderr ---\n${trimmedStderr}\n--- end stderr ---`
-        : "";
-      reject(
-        new Error(
-          `Test file ${path.relative(
-            TESTS_ROOT_PATH,
-            filePath
-          )} failed (${reason})${stderrSuffix}`
-        )
-      );
-    });
+export function runFileInSubprocess(cwd: string, filePath: string): void {
+  const { status, signal, stdout, stderr } = spawnTest(filePath, {
+    cwd,
+    nodeFlags: ["--expose-gc"],
   });
+
+  if (stdout) process.stdout.write(stdout);
+
+  if (status === 0) return;
+
+  const reason =
+    status !== null ? `exit code ${status}` : `signal ${signal ?? "unknown"}`;
+  const trimmedStderr = stderr.trim();
+  const stderrSuffix = trimmedStderr
+    ? `\n--- stderr ---\n${trimmedStderr}\n--- end stderr ---`
+    : "";
+  throw new Error(
+    `Test file ${path.relative(
+      TESTS_ROOT_PATH,
+      path.join(cwd, filePath)
+    )} failed (${reason})${stderrSuffix}`
+  );
 }

tests/harness/spawn-test-fail-child.mjs

@@ -0,0 +1,4 @@
+// Spawned by spawn-test.js. Throws an error with a recognizable marker so the
+// parent can assert that stderr was captured and that the non-zero exit status
+// is surfaced.
+throw new Error('spawn-test-fail-marker');

tests/harness/spawn-test-gc-child.mjs

@@ -0,0 +1,7 @@
+// Spawned by spawn-test.js to verify that custom nodeFlags reach the child
+// process. With --expose-gc, Node installs `gc` on globalThis; without the
+// flag, it is undefined.
+// eslint-disable-next-line no-restricted-syntax
+if (typeof globalThis.gc !== 'function') {
+  throw new Error('Expected globalThis.gc to be a function when --expose-gc is forwarded');
+}

tests/harness/spawn-test-ok-child.mjs

@@ -0,0 +1,5 @@
+// Spawned by spawn-test.js. Confirms harness globals are injected into the
+// child process by checking `assert` exists, then exits 0.
+if (typeof assert !== 'function') {
+  throw new Error('Expected `assert` to be a CTS harness global inside spawned children');
+}

tests/harness/spawn-test.js

@@ -0,0 +1,55 @@
+// spawnTest is a function
+if (typeof spawnTest !== 'function') {
+  throw new Error('Expected a global spawnTest function');
+}
+
+// Successful child: exits 0, stderr empty, and harness globals are available
+// inside the child (the child checks `typeof assert === 'function'` itself).
+{
+  const result = spawnTest('spawn-test-ok-child.mjs');
+  assert.strictEqual(result.status, 0, `ok child exited with status ${result.status}; stderr:\n${result.stderr}`);
+  assert.strictEqual(result.signal, null);
+  assert.strictEqual(result.stderr, '');
+}
+
+// Failing child: non-zero status and stderr contains the thrown marker.
+{
+  const result = spawnTest('spawn-test-fail-child.mjs');
+  assert.notStrictEqual(result.status, 0, 'fail child should exit non-zero');
+  if (!result.stderr.includes('spawn-test-fail-marker')) {
+    throw new Error(`Expected stderr to include the failure marker, got:\n${result.stderr}`);
+  }
+}
+
+// Result shape: all four fields are present.
+{
+  const result = spawnTest('spawn-test-ok-child.mjs');
+  for (const key of ['status', 'signal', 'stdout', 'stderr']) {
+    if (!(key in result)) {
+      throw new Error(`Expected spawnTest result to have "${key}" field`);
+    }
+  }
+  assert.strictEqual(typeof result.stdout, 'string');
+  assert.strictEqual(typeof result.stderr, 'string');
+}
+
+// nodeFlags are forwarded to the child: without --expose-gc the gc child
+// exits non-zero; passing it via nodeFlags makes the child exit 0.
+{
+  const withoutFlag = spawnTest('spawn-test-gc-child.mjs');
+  assert.notStrictEqual(withoutFlag.status, 0, 'gc child should fail when --expose-gc is not forwarded');
+
+  const withFlag = spawnTest('spawn-test-gc-child.mjs', { nodeFlags: ['--expose-gc'] });
+  assert.strictEqual(withFlag.status, 0, `gc child exited with status ${withFlag.status}; stderr:\n${withFlag.stderr}`);
+}
+
+// cwd is forwarded to the child: running from the parent of tests/harness
+// makes the bare child filename unresolvable. The child's stderr must name
+// the specific file Node tried to load, proving cwd actually shifted.
+{
+  const result = spawnTest('spawn-test-ok-child.mjs', { cwd: '..' });
+  assert.notStrictEqual(result.status, 0, 'expected cwd ".." to make the child filename unresolvable');
+  if (!result.stderr.includes('spawn-test-ok-child.mjs')) {
+    throw new Error(`Expected stderr to reference the unresolved child filename, got:\n${result.stderr}`);
+  }
+}