module zbuff_tb ();
parameter BITS = 4;
reg dE;
reg[BITS-1:0] dA;
wire[BITS-1:0] mY;
integer loop,ecnt;
initial begin
  ecnt = 0;
  for (loop=0;loop<2**(BITS+1);loop=loop+1) begin
    {dE,dA} = loop;
    #5;
    if (dE===1'b1) begin
      if (mY!==dA) begin
        ecnt = ecnt + 1;
      end
    end
    else if (dE===1'b0) begin
      if (mY!=={BITS{1'bz}}) begin
        ecnt = ecnt + 1;
      end
    end
    #5;
  end
  if (ecnt==0) begin
    $display("-- Module zbuff verified");
  end
  else begin
    $display("** Module zbuff with error(s) (%d)",ecnt);
  end
  $stop;
end
zbuff dut (dE,dA,mY);
endmodule