fs: added tests for util file preprocessSymlinkDestination

PR-URL: https://github.com/nodejs/node/pull/27468
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Masashi Hirano <shisama07@gmail.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>

test/parallel/test-internal-fs.js

@@ -2,6 +2,7 @@
 'use strict';
 
 const common = require('../common');
+const assert = require('assert');
 const fs = require('internal/fs/utils');
 
 // Valid encodings and no args should not throw.
@@ -12,3 +13,41 @@ common.expectsError(
   () => fs.assertEncoding('foo'),
   { code: 'ERR_INVALID_OPT_VALUE_ENCODING', type: TypeError }
 );
+
+// Test junction symlinks
+{
+  const pathString = 'c:\\test1';
+  const linkPathString = '\\test2';
+
+  const preprocessSymlinkDestination = fs.preprocessSymlinkDestination(
+    pathString,
+    'junction',
+    linkPathString
+  );
+
+  if (process.platform === 'win32') {
+    assert.strictEqual(/^\\\\\?\\/.test(preprocessSymlinkDestination), true);
+  } else {
+    assert.strictEqual(preprocessSymlinkDestination, pathString);
+  }
+}
+
+// Test none junction symlinks
+{
+  const pathString = 'c:\\test1';
+  const linkPathString = '\\test2';
+
+  const preprocessSymlinkDestination = fs.preprocessSymlinkDestination(
+    pathString,
+    undefined,
+    linkPathString
+  );
+
+  if (process.platform === 'win32') {
+    // There should not be any forward slashes
+    assert.strictEqual(
+      /\//.test(preprocessSymlinkDestination), false);
+  } else {
+    assert.strictEqual(preprocessSymlinkDestination, pathString);
+  }
+}