In this paper we continue the study of the input-output conformance simulation (iocos). In particular, we focus on implementation aspects to show that iocos is indeed an interesting semantic relation for formal methods. We address two complementary issues: a) In the context of model based testing (MBT) we present an online, also called on-the-fly, testing algorithm that checks whether an implementation conforms a given specification. Online testing combines test generation and execution and avoids the generation of the complete test suite for the specification. We prove both soundness and completeness of the online algorithm with respect to the iocos relation. b) In the context of formal verification and model checking minimisation a key issue is to efficiently compute the considered semantic relations; we show how the coinductive flavour of our conformance relation iocos makes it appropriate to be cast into an instance of the Generalised Coarsest Partition Problem (GCPP) and thus it can be efficiently computed.