Adding Jest

src/__mocks__/styleMock.js

@@ -0,0 +1 @@
+module.exports = {};

src/__mocks__/svgMock.js

@@ -0,0 +1 @@
+module.exports = () => 'mock SVG';

src/components/Message/__snapshots__/test.js.snap

@@ -0,0 +1,29 @@
+// Jest Snapshot v1, https://goo.gl/fbAQLP
+
+exports[`Message rendering 1`] = `
+<div
+  className={undefined}
+>
+  <h2>
+    
+    Testing
+  </h2>
+  <p>
+    Message content
+  </p>
+</div>
+`;
+
+exports[`Message rendering with icon 1`] = `
+<div
+  className={undefined}
+>
+  <h2>
+    Sample icon SVG
+    Testing
+  </h2>
+  <p>
+    Message content
+  </p>
+</div>
+`;

src/components/Message/index.js

@@ -12,7 +12,10 @@ const Message = ({ icon, heading, children }) => {
 };
 
 Message.propTypes = {
-  icon: PropTypes.element,
+  icon: PropTypes.oneOfType([
+    PropTypes.element,
+    PropTypes.func
+  ]),
   heading: PropTypes.string.isRequired,
   children: PropTypes.element.isRequired
 };

src/components/Message/test.js

@@ -0,0 +1,25 @@
+import React from 'react';
+import renderer from 'react-test-renderer';
+
+import Message from './index';
+
+test('Message rendering', () => {
+  const component = renderer.create(
+    <Message heading="Testing">
+      <p>Message content</p>
+    </Message>
+  );
+  let tree = component.toJSON();
+  expect(tree).toMatchSnapshot();
+});
+
+test('Message rendering with icon', () => {
+  const Icon = () => 'Sample icon SVG';
+  const component = renderer.create(
+    <Message heading="Testing" icon={ Icon }>
+      <p>Message content</p>
+    </Message>
+  );
+  let tree = component.toJSON();
+  expect(tree).toMatchSnapshot();
+});