title: Can I get Jest test instance id or context
body: <p>Suppose my test setup has the following pattern:</p>
  <ol>
  <li>Build a model for this test</li>
  <li>Initialize some application based on this model</li>
  <li>Test the functioniality in the application</li>
  </ol>
  <p>As part of #3, there are some async functions which can be run.
  I have thousands of tests and want to create a safeguard against leaks of async functions into other tests- in other words, developers who forget to await for the result</p>
  <p>My idea is as follows - Implement an afterEach in a global context which would check if an applcation instance was created for this test. If it was, I can catch all open async functions from here, and throw an error</p>
  <p>To do this, I would need to have a testId instance or test context to which I can register the app instance when creating it for tests.</p>
  <p>If we were using jasmine and old ES5 syntax, jasmine has a userContext feature which would make this easy:</p>
  <p>it('some test', async function(){
  this.appInstance = createAppInstance(model)
  ...
  })</p>
  <p>afterEach(function(){
  if(this.appInstance){
  ...
  }
  })</p>
  <p>Is there a way to do something like this in jest?</p>