Try to skip the test , using export DH_RUBY_IGNORE_TESTS = all and checking it in sbuild if its running well.
Thank you, that solved. But i'm just wondering now, what would be the better approach, to ignore tests or to override the build target and prepare the environment to run the tests?
The process of "preparing the environment" consist of:
mkdir -p /tmp/fakehome/.wpscan
# unzip before tests because tests need data
unzip -o data.zip -d /tmp/fakehome/.wpscan/
HOME=/tmp/fakehome RUBYLIB=$(CURDIR)/lib ruby debian/ruby-tests.rb