  The right to contest a decision with consequences on individuals or the
society is a well-established democratic right. Despite this right also being
explicitly included in GDPR in reference to automated decision-making, its
study seems to have received much less attention in the AI literature compared,
for example, to the right for explanation. This paper investigates the type of
assurances that are needed in the contesting process when algorithmic
black-boxes are involved, opening new questions about the interplay of
contestability and explainability. We argue that specialised complementary
methodologies to evaluate automated decision-making in the case of a particular
decision being contested need to be developed. Further, we propose a
combination of well-established software engineering and rule-based approaches
as a possible socio-technical solution to the issue of contestability, one of
the new democratic challenges posed by the automation of decision making.
