Catastrophic impacts of Near-Earth Asteroids (NEAs) on our planet are believed to be avoidable, if the resources to launch adeflection mission can be made available. In order to guarantee a successful threat mitigation operation, the role of uncertaintiesin the physical and orbital parameters of NEAs on the deflectionoutcome needs to be understood. Conducting deflectiondemonstration missions is essential in this respect, as they offer the opportunity to test our current understanding of the processes governing, for instance, kinetic impacts and gravity tractoring. In this contribution we discuss prerequisites and time frames for deflection test mission scenarios elaborated in the NEOShield project that will render such efforts as cost effective and as safe as possible.