Issue 396 - Add a test for fs.promises.stat() when the path does not exist (#406)

* test non exist path for promise

* fix new line at the end

* fix missing semicolon 113:26

* follow 'Testing promise codes' on guidline

tests/spec/fs.stat.spec.js

@@ -121,3 +121,22 @@ describe('fs.stat', function() {
       }); 
   });
 });
+
+/**
+ * fsPromises tests
+ */
+
+describe('fsPromises.stat', function() {
+  beforeEach(util.setup);
+  afterEach(util.cleanup);
+
+  it('should return an error if path does not exist', function() {
+    var fsPromises = util.fs().promises;
+
+    return fsPromises.stat('/tmp')
+      .catch(error => {
+        expect(error).to.exist;
+        expect(error.code).to.equal('ENOENT');
+      });
+  });
+});