Re: [PATCH 1/6] t/checkout-last: checkout - doesn't work after rebase

Junio C Hamano wrote:

Why two?

What breaks checkout - is the initial HEAD detachment (which writes
that "checkout: " message), before anything else happens.  None of
<onto>, <upstream>, and <branch> make any difference: I'm testing
exactly the code that I patched.

I have recently been told that I should be testing "end-user behavior"
by treating the programs as black-boxes, instead of "implementation".
What is your opinion on the issue?  Should I write more tests?