The issue is that this is a third party framework that does not have tests itself. It is also encapsulated, so it is not trivial to add tests externally. 

I will investigate if I can detect the number of vm_allocate calls via a documented Apple API and then check that from a Chromium browser test.

The following revision refers to this bug:
  https://chromium.googlesource.com/chromium/src.git/+/42f65bb56932d7145280f3ba86e0216b7bbdca13

commit 42f65bb56932d7145280f3ba86e0216b7bbdca13
Author: Boris Vidolov <borisv@chromium.org>
Date: Mon Jul 31 22:38:37 2017

Add tests for EnableCFBundleBlocker and track allocation attempts for mach_override_ptr.
Bug:737938

Change-Id: I5cc819ed87b4ba5ec292a001ada15df24c0042e7
Reviewed-on: https://chromium-review.googlesource.com/592110
Commit-Queue: Boris Vidolov <borisv@chromium.org>
Reviewed-by: Mark Mentovai <mark@chromium.org>
Cr-Commit-Position: refs/heads/master@{#490809}
[modify] https://crrev.com/42f65bb56932d7145280f3ba86e0216b7bbdca13/chrome/common/mac/cfbundle_blocker.h
[modify] https://crrev.com/42f65bb56932d7145280f3ba86e0216b7bbdca13/chrome/common/mac/cfbundle_blocker.mm
[add] https://crrev.com/42f65bb56932d7145280f3ba86e0216b7bbdca13/chrome/common/mac/cfbundle_blocker_private.h
[modify] https://crrev.com/42f65bb56932d7145280f3ba86e0216b7bbdca13/chrome/common/mac/cfbundle_blocker_unittest.mm
[modify] https://crrev.com/42f65bb56932d7145280f3ba86e0216b7bbdca13/third_party/mach_override/README.chromium
[modify] https://crrev.com/42f65bb56932d7145280f3ba86e0216b7bbdca13/third_party/mach_override/chromium.patch
[modify] https://crrev.com/42f65bb56932d7145280f3ba86e0216b7bbdca13/third_party/mach_override/mach_override.c
[modify] https://crrev.com/42f65bb56932d7145280f3ba86e0216b7bbdca13/third_party/mach_override/mach_override.h