Solar System is one of the best laboratories to test General Relativity (GR). We give a complete overview of what has been done during the last decade, focusing on space & ground geodesy as well as on deep space navigation, by considering two different frameworks : the traditional Parametrized Post-Newtonian (PPN) approach and the Standard Model Extension (SME), enabling one to study in full detail possible violations of Lorentz symmetry. After discussing recent constraints obtained from Lunar Laser Ranging, Very Long Baseline Interferometry and planetary ephemerides, we will consider what can be expected from the Gaia mission. Launched by the European Space Agency in late December 2013, its main objective is to survey one billion stars of our Galaxy. Gaia will also observe more than 360000 Solar System Objects (SSO). Due to its unprecedented accuracy of a few micro-arcseconds, Gaia data processing necessitates full relativistic modelling. It opens the door to several GR tests. We will present first how light bending effects can improve our current knowledge of the PPN Gamma Parameter. We will then present SSO simulations highlighting a sensitivity study on various gravitational tests, in particular concerning fifth force and SME formalisms.