Fix running tests with Typescript

Author: kristerkari

__tests__/App.js

@@ -0,0 +1,10 @@
+import React from "react";
+import "react-native";
+// Note: test renderer must be required after react-native.
+import renderer from "react-test-renderer";
+import App from "../src/App";
+
+it("renders correctly", () => {
+  const tree = renderer.create(<App />);
+  expect(tree).toMatchSnapshot();
+});