Refactored ServerError to infer error message based on provided server type guards

test/common/ErrorHandler.test.tsx

@@ -0,0 +1,38 @@
+import React from 'react';
+import { shallow, ShallowWrapper } from 'enzyme';
+import { Button } from 'reactstrap';
+import { Mock } from 'ts-mockery';
+import createErrorHandler from '../../src/common/ErrorHandler';
+
+describe('<ErrorHandler />', () => {
+  const window = Mock.of<Window>({
+    location: {
+      reload: jest.fn(),
+    },
+  });
+  const console = Mock.of<Console>({ error: jest.fn() });
+  let wrapper: ShallowWrapper;
+
+  beforeEach(() => {
+    const ErrorHandler = createErrorHandler(window, console);
+
+    wrapper = shallow(<ErrorHandler children={<span>Foo</span>} />);
+  });
+
+  afterEach(() => wrapper.unmount());
+
+  it('renders children when no error has occurred', () => {
+    expect(wrapper.text()).toEqual('Foo');
+    expect(wrapper.find(Button)).toHaveLength(0);
+  });
+
+  it('renders error page when error has occurred', () => {
+    wrapper.setState({ hasError: true });
+
+    expect(wrapper.text()).toContain('Oops! This is awkward :S');
+    expect(wrapper.text()).toContain(
+      'It seems that something went wrong. Try refreshing the page or just click this button.',
+    );
+    expect(wrapper.find(Button)).toHaveLength(1);
+  });
+});