Add fake_date test helper and use it in spec

#236004

ee/spec/frontend/threat_monitoring/components/__snapshots__/network_policy_list_spec.js.snap

@@ -90,7 +90,7 @@ exports[`NetworkPolicyList component renders policies table 1`] = `
       >
         <div>
           
-      4 months ago
+      2 months ago
     
         </div>
       </td>

ee/spec/frontend/threat_monitoring/components/network_policy_list_spec.js

@@ -5,11 +5,14 @@ import { GlTable } from '@gitlab/ui';
 import { convertObjectPropsToCamelCase } from '~/lib/utils/common_utils';
 
 import { mockPoliciesResponse } from '../mock_data';
+import { useFakeDate } from 'helpers/fake_date';
 import { PREDEFINED_NETWORK_POLICIES } from 'ee/threat_monitoring/constants';
 
 const mockData = mockPoliciesResponse.map(policy => convertObjectPropsToCamelCase(policy));
 
 describe('NetworkPolicyList component', () => {
+  useFakeDate();
+
   let store;
   let wrapper;
 

spec/frontend/helpers/fake_date.js

+import { memoize } from 'lodash';
+
+// Frida Kahlo's birthday (6 = July)
+const DEFAULT_PARAM = [2020, 6, 6];
+
+const createFakeDateClass = memoize(ctorDefault => {
+  class FakeDate extends Date {
+    constructor(...ctorArgs) {
+      const args = ctorArgs.length ? ctorArgs : ctorDefault;
+
+      super(...args);
+    }
+
+    static now() {
+      return new FakeDate().getTime();
+    }
+  }
+
+  return FakeDate;
+});
+
+let isUsingFake = false;
+let origDate = Date;
+
+export const useFakeDate = (...args) => {
+  if (isUsingFake) {
+    throw new Error('Unexpected call to useFakeDate! Already using fake date.');
+  }
+
+  const FakeDate = createFakeDateClass(args.length ? args : DEFAULT_PARAM);
+  origDate = global.Date;
+  global.Date = FakeDate;
+  isUsingFake = true;
+};
+
+export const useRealDate = () => {
+  if (!isUsingFake) {
+    throw new Error('Unexpected call to useRealDate! Already using real date.');
+  }
+
+  global.Date = origDate;
+  isUsingFake = false;
+};