  We provide an irreducibility test in the ring K[[x]][y] whose complexity is
quasi-linear with respect to the discriminant valuation, assuming the input
polynomial F square-free and K a perfect field of characteristic zero or
greater than deg(F). The algorithm uses the theory of approximate roots and may
be seen as a generalisation of Abhyankhar's irreducibility criterion to the
case of non algebraically closed residue fields.
