vm: increase code coverage of source_text_module.js

PR-URL: #28350
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

test/parallel/test-vm-module-dynamic-namespace.js

@@ -0,0 +1,35 @@
+'use strict';
+
+// Flags: --experimental-vm-modules --expose-internals
+//
+const common = require('../common');
+
+const assert = require('assert');
+
+const { types } = require('util');
+const { SourceTextModule, wrapMap } = require('internal/vm/source_text_module');
+
+const { importModuleDynamicallyCallback } =
+  require('internal/process/esm_loader');
+
+async function getNamespace() {
+  const m = new SourceTextModule('');
+  await m.link(() => 0);
+  m.instantiate();
+  await m.evaluate();
+  return m.namespace;
+}
+
+(async () => {
+  const namespace = await getNamespace();
+  const m = new SourceTextModule('export const A = "A";', {
+    importModuleDynamically: common.mustCall((specifier, wrap) => {
+      return namespace;
+    })
+  });
+  await m.link(() => 0);
+  m.instantiate();
+  await m.evaluate();
+  const ns = await importModuleDynamicallyCallback(wrapMap.get(m));
+  assert.ok(types.isModuleNamespaceObject(ns));
+})().then(common.mustCall());