only print file information if actually provided

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>
expose _tap_vok with tap_vok wrapper

Make it easier for users to write their own test helpers

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>
remove trailing whitespace

Signed-off-by: Andrew Gregory <andrew.gregory.8@gmail.com>