dropdown unit testing

Author: mylee1995

src/app/__tests__/dropdown.test.js

@@ -0,0 +1,38 @@
+import React from 'react';
+import { configure, shallow } from 'enzyme';
+import Adapter from 'enzyme-adapter-react-16';
+import Dropdown from '../components/Dropdown';
+
+configure({ adapter: new Adapter() });
+
+describe('unit testing for Dropdown.jsx', () => {
+    let wrapper;
+    const props = {
+        options: [
+            { value: 2000, label: '0.5x' },
+            { value: 1000, label: '1.0x' },
+            { value: 500, label: '2.0x' },
+          ],
+        handleChangeSpeed: jest.fn(),
+        selectedOption: { value: 1000, label: '1.0x' }
+    };
+    beforeEach(() => {
+        wrapper = shallow(<Dropdown {...props} />);
+    });
+
+    describe('Component', () => {
+        test('array of objects that have value and label should be options props', () => {
+            expect(wrapper.props().options).toEqual(props.options);
+        });
+        test('selectedOption should be value property', () => {
+            expect(wrapper.props().value).toEqual(props.selectedOption);
+        })
+    })
+
+    describe('handlechangeSpeed', () => {
+        test('should invoke handleChangeSpeed onChange', () => {
+            wrapper.simulate('change', { value: 2000, label: '0.5x' });
+            expect(props.handleChangeSpeed).toHaveBeenCalled();
+        });
+    });
+});