Add missing unit tests to JavaScript and React components (#5505)

Add the missing unit tests login, bucket listing, and bucket searching functionalities.

browser/app/js/components/__tests__/App.test.js

@@ -0,0 +1,25 @@
+/*
+ * Minio Cloud Storage (C) 2018 Minio, Inc.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+
+import React from "react"
+import { shallow } from "enzyme"
+import App from "../App"
+
+describe("App", () => {
+  it("should render without crashing", () => {
+    shallow(<App match={ {url: "/minio"} }/>)
+  })
+})