Add some tests for the Button component

Author: jakezatecky

src/js/Button.js

@@ -4,7 +4,11 @@ import React from 'react';
 class Button extends React.PureComponent {
     static propTypes = {
         children: PropTypes.node.isRequired,
-        title: PropTypes.string.isRequired,
+        title: PropTypes.string,
+    };
+
+    static defaultProps = {
+        title: null,
     };
 
     render() {

test/Button.js

@@ -0,0 +1,39 @@
+import React from 'react';
+import { shallow } from 'enzyme';
+import { assert } from 'chai';
+
+import Button from '../src/js/Button';
+
+describe('<Button />', () => {
+    describe('title', () => {
+        it('should copy `title` to `aria-label`', () => {
+            const wrapper = shallow((
+                <Button title="Collapse">
+                    Collapse
+                </Button>
+            ));
+
+            assert.equal('Collapse', wrapper.find('button').prop('aria-label'));
+        });
+
+        it('should set `type` to `button`', () => {
+            const wrapper = shallow((
+                <Button>
+                    Basic Button
+                </Button>
+            ));
+
+            assert.equal('button', wrapper.find('button').prop('type'));
+        });
+
+        it('should pass extra properties to the base button', () => {
+            const wrapper = shallow((
+                <Button className="btn">
+                    Basic Button
+                </Button>
+            ));
+
+            assert.equal('btn', wrapper.find('button').prop('className'));
+        });
+    });
+});