High-tech systems come in many variants, customized for various users. These systems evolve over time to adapt to changing requirements and contexts. The number of possible different variants grows exponentially making testing of systems with high variability and evolution a major challenge. The TiCToC project investigates methods and tools to manage and reduce the combinatorial explosion of testing complex hightech systems. The aim is that not all versions and variants have to be completely re-tested, while still providing high, argued test coverage and confidence in the quality of the whole system. TiCToC will follow a model-based approach using component-based and feature-driven testing. Topics that are addressed include: modelling and decomposition of a system into components and features, compositional testing, impact analysis of system modifications, minimization of re-testing after a change, automatic test generation from models and usage data, and representation of models and testing concepts in an intuitive and human-accessible form in domain-specific languages.