  The study of the top quark properties will be an integral part of any
particle physics activity at future leptonic colliders. In this proceeding we
discuss the possibility of testing composite Higgs scenarios at $e^+e^-$
prototypes through deviations from the Standard Model predictions in $t\bar t$
production observables for various centre of mass energies, ranging from 370
GeV up to 1 TeV. This proceedings draws from Ref. arXiv:1504.05407
