In `test_helper.bash`:
set
PATH="${BATS_TEST_DIRNAME%/*}/libexec:$PATH"
instead of
PATH="${BATS_TEST_DIRNAME}../libexec:$PATH"
it essentially enables us to expect
`${exec_root}/completions/pyenv.bash`
instead of something like
`${exec_root}/test/../completions/pyenv.zsh
b1882cb6fe