Add unit tests for helpers methods

[kararade]

Release Type: Dev Improvement

Fixes https://github.com/x-team/xp/issues/2017

Description

Unit tests added for the helper methods of XP-UI

Checklist

Before submitting a pull request, please make sure the following is done:

• set yourself as an assignee
• set appropriate labels for a PR (In Review or In Progress depending on its status)
• make sure your code lints (npm run lint)
• Flow typechecks passed (npm run flow)
• Snapshots tests passed (npm run jest) (NOTE: This is temporarily disabled. Skip it.)
• check cleanup tasks (https://github.com/x-team/xp/labels/cleanup) and take a suitable small one (if exists) in a related area of the current changes
• if any snapshots have been changed, verify that component still works and looks as expected and update the changed snapshot (NOTE: This is temporarily disabled. Skip it.)
• once finished with all the changes, you run npm run build command and committed changed files to the branch
• manually tested the app by running it in several different browsers (Firefox, Chrome, Opera, Safari, MS IE/Edge, etc.) and checked nothing is broken and operates as expected!

Steps to Test or Reproduce

1. Run rm -r node_dependencies && npm i
2. Run npm run jest
3. Confirm that the unit tests added for the helpers methods all pass

Impacted Areas in Application

• src/utils/helpers.js - added comments and removed dead methods

1. getOlderBrowserErrorKey()- refactored
2. timeSince()- refactored

• _tests_/utils/helpers.spec.js - created
• .jest/setupTests.js - refactored

Screenshots

1. Affected by timeSince() helper method refactored

• /src/components/ui/ActivityBar.js

• /src/components/ui/Email.js

• /src/components/ui/EmailFeed.js

• /src/components/ui/Note.js

2. Affected by getOlderBrowserErrorKey() helper method refactored

• /src/components/ui/ErrorBox.js

[nicksp]

Let's clean up a little bit.