       last = now
 
       if diff isnt Infinity
-        diff.should.be.within duration, duration + 10
+        diff.should.be.approximately duration, 10
 
       switch count++
 


      _fn = (args) ->
        diff = Date.now() - start
        diff.should.be.within output[i], output[i] + 7
        if i is output.length - 1 then complete()
        i++



    promise.then ->
      diff = Date.now() - start
      diff.should.be.approximately duration, 10
      done()


