  Quality and reliability metrics play an important role in the evaluation of
the state of a system during the development and testing phases, and serve as
tools to optimize the testing process or to define the exit or acceptance
criteria of the system. This study provides a consolidated view on the
available quality and reliability metrics applicable to Internet of Things
(IoT) systems, as no comprehensive study has provided such a view specific to
these systems. The quality and reliability metrics categorized and discussed in
this paper are divided into three categories: metrics assessing the quality of
an IoT system or service, metrics for assessing the effectiveness of the
testing process, and metrics that can be universally applied in both cases. In
the discussion, recommendations of proper usage of discussed metrics in a
testing process are then given.
