Unify test harness set up

[AndreasArvidsson]

Today the recorded test has the context/snapshot needed for the test case. This api should be available for manual test as well. Preferably mocked settings would be added to this api surface.

setupTest({
  language: "javascript",
  documentContent: "hello world",
  selections: [],
  settings: {
    commandHistory: true
  }
})