test: fix snapshot test

The snapshot test included footer, which uses the Date object for the copyright data.
This fix mocks the Date object in the test so that it doesn't change.

Author: jonoliver

__tests__/snapshot.js

@@ -3,6 +3,9 @@ import renderer from 'react-test-renderer';
 import Index from '../pages/index';
 
 it('renders homepage unchanged', () => {
+  const mockFooterDate = new Date(2023, 0, 1);
+  jest.spyOn(global, 'Date').mockImplementation(() => mockFooterDate);
+
   const apprenticeData = {
     currentApprenticeGroup: {
       version: '0.0',