gtk3 test: check min and max values at once
gtk3 test: check min and max values at once

They are strongly associated values. So it is natural that we check
them at once.

There is another advantage for the check. We can check max value even
if min value check is failed.

kitachro/ruby-gnome2,kitachro/ruby-gnome2,kitachro/ruby-gnome2,kitachro/ruby-gnome2,kitachro/ruby-gnome2