test: reproduce failing upper path test

In an attempt to reproduce the test case presented in #167

test/fs.spec.js

@@ -89,6 +89,16 @@ describe('FileSystem', function () {
         nodePath.resolve('/tmp/ftp-srv'));
     });
 
+    it('cannot escape root - win, escaped', function () {
+      // eslint-disable-next-line no-useless-escape
+      const result = fs._resolvePath('\/../../../');
+      expect(result).to.be.an('object');
+      expect(result.clientPath).to.equal(
+        nodePath.normalize('/'));
+      expect(result.fsPath).to.equal(
+        nodePath.resolve('/tmp/ftp-srv'));
+    });
+
     it('cannot escape root - backslash prefix', function () {
       const result = fs._resolvePath('\\/../../../../../../');
       expect(result).to.be.an('object');