title: Jest jenkins coverage
body: <p>So i'm running test for jest successfully in Jenkins. Now we have some old projects that have zero coverage on them and i would like to start collecting coverage on changed files.</p>
  
  <p>So here is my scenario, today i have 0% coverage over lets 100 lines of code, tomorrow i add 10 lines of code now i want to make sure that there is proper coverage for the 10 newly added lines of code.</p>
  
  <p>If there is no coverage for the 10 new lines then i want to fail the build and force the developer to write test case.</p>
  
  <p>If it is not possible on a line level i could also deal with file level, so if a file has changed it needs to have coverage for example.</p>
  
  <p>Is something like this possible?</p>