  The homologation of automated vehicles, being safety-critical complex
systems, requires sound evidence for their safe operability. Traditionally,
verification and validation activities are guided by a combination of ISO 26262
and ISO/PAS 21448, together with distance-based testing. Starting at SAE Level
3, such approaches become infeasible, resulting in the need for novel methods.
Scenario-based testing is regarded as a possible enabler for verification and
validation of automated vehicles. Its effectiveness, however, rests on the
consistency and substantiality of the arguments used in each step of the
process. In this work, we sketch a generic framework around scenario-based
testing and analyze contemporary approaches to the individual steps. For each
step, we describe its function, discuss proposed approaches and solutions, and
identify the underlying arguments, principles and assumptions. As a result, we
present a list of fundamental considerations for which evidences need to be
gathered in order for scenario-based testing to support the homologation of
automated vehicles.
