Operating system: Windows 8.1
PlatformIO Version (platformio --version): PlatformIO, version 3.6.0
[A] We can see this bug directly on the tutorial documentation here (so you can follow these steps to reproduce them) :

As you can see there is 11 tests that have run, and only 6 are displayed. There is also 1 failure which is not desplayed.
So as we can see the bug is that the unit testing module doesn't display all the results, this is a bug. Besides, there is a failure, I don't know if it is a real one, but this failure is not displayed.
[B] Note also that "1 Failures" (instead of "1 Failure" or "1 Failure(s)") is a grammatical error.
[C] It will be good and more coherent if the test abstract shows "11 Test(s) 1 Failure(s) 10 Passed 0 Ignored" and not only "11 Test(s) 1 Failure(s) 0 Ignored".
This issue is linked to this documentation issue : https://github.com/platformio/platformio-docs/issues/33
And we see the same things ath this webpage:
https://docs.platformio.org/en/latest/tutorials/core/unit_testing_blink.html

this one is solved by the documentation, 2 sec of delay
Thanks! Docs also should be fixed.