Fix.

node_modules/mkdirp/test/root.js

@@ -0,0 +1,19 @@
+var mkdirp = require('../');
+var path = require('path');
+var fs = require('fs');
+var test = require('tap').test;
+var _0755 = parseInt('0755', 8);
+
+test('root', function (t) {
+    // '/' on unix, 'c:/' on windows.
+    var file = path.resolve('/');
+
+    mkdirp(file, _0755, function (err) {
+        if (err) throw err
+        fs.stat(file, function (er, stat) {
+            if (er) throw er
+            t.ok(stat.isDirectory(), 'target is a directory');
+            t.end();
+        })
+    });
+});