Running make test on master using Emacs master compiled with native-comp
support throws error:

decode-time((22352 22528) nil nil)
  time-to-days((22352 22528))
  org-time-stamp-to-now("2016-06-03 Fri")
  org-deadline-close-p("2016-06-03 Fri" 0)
  apply(org-deadline-close-p ("2016-06-03 Fri" 0))

As discussed in Emacs bug#48133, this is because of outdated cl-letf
statement in org-test. The attached patch is fixing the problem.

Best,
Ihor