Mock prototype in unit test to prevent relative date breaking snapshots. (#73531)

Author: justinkambic

x-pack/plugins/uptime/public/components/common/charts/__tests__/ping_histogram.test.tsx

@@ -7,8 +7,13 @@
 import React from 'react';
 import { PingHistogramComponent, PingHistogramComponentProps } from '../ping_histogram';
 import { renderWithRouter, shallowWithRouter, MountWithReduxProvider } from '../../../../lib';
+import moment from 'moment';
 
 describe('PingHistogram component', () => {
+  beforeAll(() => {
+    moment.prototype.fromNow = jest.fn(() => 'a year ago');
+  });
+
   const props: PingHistogramComponentProps = {
     absoluteStartDate: 1548697920000,
     absoluteEndDate: 1548700920000,