test: add Windows-specific VFS mount path tests

Add test-vfs-windows.js to verify VFS mounting with Windows
drive letter paths. Tests include:

- Mounting at paths with drive letters (e.g., C:\temp\vfs-test)
- Mounting at drive root (e.g., C:\vfs-test-root)
- Verifying mountPoint returns Windows-style absolute path
- Require from Windows VFS paths

Author: mcollina

test/parallel/test-vfs-windows.js

@@ -0,0 +1,100 @@
+'use strict';
+
+const common = require('../common');
+
+if (!common.isWindows) {
+  common.skip('Windows-specific test');
+}
+
+const assert = require('assert');
+const fs = require('fs');
+const path = require('path');
+const vfs = require('node:vfs');
+
+// Test mounting with Windows drive letter path
+{
+  const myVfs = vfs.create();
+  myVfs.writeFileSync('/data.txt', 'Hello from VFS');
+  myVfs.mkdirSync('/subdir');
+  myVfs.writeFileSync('/subdir/nested.txt', 'Nested content');
+
+  // Mount at a Windows path with drive letter
+  const mountPath = path.join(process.env.TEMP || 'C:\\temp', 'vfs-test-mount');
+  myVfs.mount(mountPath);
+
+  assert.strictEqual(myVfs.mounted, true);
+  assert.strictEqual(myVfs.mountPoint, mountPath);
+
+  // Read file through fs module using Windows path
+  const content = fs.readFileSync(path.join(mountPath, 'data.txt'), 'utf8');
+  assert.strictEqual(content, 'Hello from VFS');
+
+  // Read nested file
+  const nestedContent = fs.readFileSync(path.join(mountPath, 'subdir', 'nested.txt'), 'utf8');
+  assert.strictEqual(nestedContent, 'Nested content');
+
+  // Stat operations
+  const stat = fs.statSync(path.join(mountPath, 'data.txt'));
+  assert.strictEqual(stat.isFile(), true);
+
+  const dirStat = fs.statSync(path.join(mountPath, 'subdir'));
+  assert.strictEqual(dirStat.isDirectory(), true);
+
+  // Readdir
+  const entries = fs.readdirSync(mountPath);
+  assert.deepStrictEqual(entries.sort(), ['data.txt', 'subdir']);
+
+  myVfs.unmount();
+  assert.strictEqual(myVfs.mounted, false);
+}
+
+// Test mounting at drive root (e.g., C:\virtual)
+{
+  const myVfs = vfs.create();
+  myVfs.writeFileSync('/test.txt', 'Drive root test');
+
+  // Use current drive letter
+  const driveLetter = process.cwd().slice(0, 2); // e.g., "C:"
+  const mountPath = driveLetter + '\\vfs-test-root';
+  myVfs.mount(mountPath);
+
+  assert.strictEqual(myVfs.mounted, true);
+
+  const content = fs.readFileSync(mountPath + '\\test.txt', 'utf8');
+  assert.strictEqual(content, 'Drive root test');
+
+  myVfs.unmount();
+}
+
+// Test that mountPoint returns Windows-style absolute path
+{
+  const myVfs = vfs.create();
+  myVfs.writeFileSync('/file.txt', 'content');
+
+  const mountPath = 'C:\\virtual';
+  myVfs.mount(mountPath);
+
+  // mountPoint should be an absolute Windows path
+  assert.ok(myVfs.mountPoint.includes(':'), 'mountPoint should contain drive letter');
+  assert.ok(path.isAbsolute(myVfs.mountPoint), 'mountPoint should be absolute');
+
+  myVfs.unmount();
+}
+
+// Test require from Windows VFS path
+{
+  const myVfs = vfs.create();
+  myVfs.writeFileSync('/module.js', 'module.exports = { value: 42 };');
+
+  const mountPath = path.join(process.env.TEMP || 'C:\\temp', 'vfs-require-test');
+  myVfs.mount(mountPath);
+
+  const modulePath = path.join(mountPath, 'module.js');
+  const mod = require(modulePath);
+  assert.strictEqual(mod.value, 42);
+
+  myVfs.unmount();
+
+  // Clean up require cache
+  delete require.cache[modulePath];
+}