module tb_inverter();
   reg a;
   wire y;
   inverter myinverter(a, y);
   initial begin
      $display("hello, world");
      $dumpfile("inverter.vcd");
      $dumpvars();
      $monitor("Time %0d inverter input %d output %d\n", $time, myinverter.a, myinverter.y);

      a = 0;
      #1
	a = 1;
      #2
	a = 0;
      #1
	$finish;
   end
endmodule