\(	\)

Remove[Assert];
Assert[
          b_? (Not[
                  TrueQ[#]] &)] := (Interrupt[]);
Assert[___] := {};

Remove[f];
f[x_? (IntegerQ[#]  &&  # < 1) &] := 
        Print["Entier"];
f[x_ ? (# ≤  0  &)] := 
        Print["<= 0"];
f[x_ ? (# > 0  &)] := 
        Print["> 0"];
f[___] := (Assert[False])
?f

f[-1]
f[1]
f[0]
f[-1. ]
f[1. ]
f[0. ]

f[a]