Clean up test from #1915

[compulim]

Cleaning up test from #1915:

• Only put things that are useful for > 80% of tests in /__tests__/setup/web/index.html
  • This one does not hit the bar because turning the focus yellow is only meaningful for one of the many test cases
  • Try very best not to touch the DOM when doing setup
• Put the test in its own file
  • basic.js is for really basic stuff, like, if Web Chat can be loaded or not (i.e. setup test)
  • basic.js acts as the first gate to check if everything is broken
  • More clean up over basic.js need to be done later
• Added createStyleSet option to main()
  • This will allow other tests modify style set, in addition to style options
  • If tests prefer, they can pass styleSet instead of the new createStyleSet function
  • styleSet is designed to be serializable with flat hierarchy
  • We use createStyleSet here because we want the new style set to based on Web Chat's default, i.e. need to call window.WebChat.createStyleSet(styleOptions), then customize the result
  • We can't use spread/rest because the way the file is compiled, Object.assign is used instead
• Test name should help debug future regressions
  • Our tests are based on stories, i.e. what user expect to work
  • Using story summary as test name is a good start for finding a good name

[coveralls]

Coverage remained the same at 57.502% when pulling 832d9e5 on compulim:update-sendbox-focus-test into 8c8e2cc on Microsoft:master.