test: rewrite test-child-process-spawn-args

- Use ESM for top-level await
- Avoid concurrent child processes in the test
- Use `events.once` instead of Promise wrapper
- Assert directly on sets

PR-URL: #58546
Reviewed-By: Yagiz Nizipli <yagiz@nizipli.com>
Reviewed-By: LiviaMedeiros <livia@cirno.name>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>

Author: targos

test/parallel/test-child-process-spawn-args.js

@@ -0,0 +1,50 @@
+// This test confirms that `undefined`, `null`, and `[]`
+// can be used as a placeholder for the second argument (`args`) of `spawn()`.
+// Previously, there was a bug where using `undefined` for the second argument
+// caused the third argument (`options`) to be ignored.
+// See https://github.com/nodejs/node/issues/24912.
+
+import * as common from '../common/index.mjs';
+import tmpdir from '../common/tmpdir.js';
+
+import assert from 'node:assert';
+import { spawn } from 'node:child_process';
+import { once } from 'node:events';
+
+tmpdir.refresh();
+
+const command = common.isWindows ? 'cd' : 'pwd';
+const options = { cwd: tmpdir.path };
+
+if (common.isWindows) {
+  // This test is not the case for Windows based systems
+  // unless the `shell` options equals to `true`
+  options.shell = true;
+}
+
+const testCases = [
+  undefined,
+  null,
+  [],
+];
+
+const expectedResult = new Set([tmpdir.path.trim().toLowerCase()]);
+
+const actualResults = new Set();
+
+for (const testCase of testCases) {
+  const subprocess = spawn(command, testCase, options);
+
+  let accumulatedData = '';
+
+  subprocess.stdout.setEncoding('utf8');
+  subprocess.stdout.on('data', common.mustCall((data) => {
+    accumulatedData += data;
+  }));
+
+  await once(subprocess.stdout, 'end');
+
+  actualResults.add(accumulatedData.trim().toLowerCase());
+}
+
+assert.deepStrictEqual(actualResults, expectedResult);