Why a missile test needs secrecy? It provides a deterrence. More your "enemies" know about your capabilities, more you can keep them at bay.
To some degree that is true but don't be so naive friend. When you have an adversary that is counting the days to launch an attack when you are least prepared.....known capabilities become a weak point that get exploited. It allows your potential adversary to build countermeasures to defeat your weapon platforms. Once this happens, the question won;t be whether you will lose the war but how much will lose!