Add tests for 'Button' component

Close #583

src/components/Button/__tests__/index-test.js

@@ -1,5 +1,30 @@
 /* eslint-env jasmine, jest */
 
+import React from 'react';
+import Button from '..';
+import { mount, shallow } from 'enzyme';
+
+const findNativeButton = wrapper => wrapper.getDOMNode();
+
 describe('components/Button', () => {
-  test.skip('NO TEST COVERAGE', () => {});
+  test('prop "color"', () => {
+    const onPress = () => {};
+    const color = 'blue';
+    const button = findNativeButton(mount(<Button color={color} onPress={onPress} title="" />));
+    expect(button.style.backgroundColor).toEqual(color);
+  });
+
+  test('prop "onPress"', () => {
+    const onPress = jest.fn();
+    const component = shallow(<Button onPress={onPress} title="" />);
+    component.simulate('press');
+    expect(onPress).toHaveBeenCalled();
+  });
+
+  test('prop "title"', () => {
+    const onPress = () => {};
+    const text = 'Click me';
+    const component = mount(<Button onPress={onPress} title={text} />);
+    expect(component.text()).toEqual(text);
+  });
 });