add a unit test using Enzyme for Display component

__tests__/src/components/Display.test.js

+import React from 'react';
+import { shallow } from 'enzyme';
+import Display from '../../../src/components/Display';
+
+describe('Display', () => {
+  it('renders without an error', () => {
+    const wrapper = shallow(<Display manifest={{}} />);
+    expect(wrapper.contains(<div className="Display"><pre id="exampleManifest" className="" /></div>)).toBe(true);
+  });
+  it('sets class based on manifest state', () => {
+    let wrapper = shallow(<Display manifest={{ isFetching: true }} />);
+    expect(wrapper.find('.fetching').length).toBe(1);
+
+    wrapper = shallow(<Display manifest={{ error: true }} />);
+    expect(wrapper.find('.error').length).toBe(1);
+  });
+  it('displays content', () => {
+    let wrapper = shallow(<Display manifest={{ isFetching: true }} />);
+    expect(wrapper.text()).toBe('☕');
+
+    wrapper = shallow(<Display manifest={{ error: { message: 'bad things' } }} />);
+    expect(wrapper.text()).toBe('bad things');
+
+    wrapper = shallow(<Display manifest={{ json: { iiif: 'manifest' } }} />);
+    expect(JSON.parse(wrapper.text())).toEqual({ iiif: 'manifest' });
+  });
+});

package.json

@@ -32,6 +32,8 @@
     "babel-preset-env": "^1.7.0",
     "babel-preset-react": "^6.24.1",
     "css-loader": "^1.0.0",
+    "enzyme": "^3.4.4",
+    "enzyme-adapter-react-16": "^1.2.0",
     "eslint": "^4.18.2",
     "eslint-config-airbnb": "^16.1.0",
     "eslint-loader": "^1.9.0",

setupJest.js

 // Setup Jest to mock fetch
 
 import fetch from 'jest-fetch-mock'; // eslint-disable-line import/no-extraneous-dependencies
+import Enzyme from 'enzyme'; // eslint-disable-line import/no-extraneous-dependencies
+import Adapter from 'enzyme-adapter-react-16'; // eslint-disable-line import/no-extraneous-dependencies
 
 jest.setMock('node-fetch', fetch);
 global.fetch = require('jest-fetch-mock'); // eslint-disable-line import/no-extraneous-dependencies
+
+Enzyme.configure({ adapter: new Adapter() });