blinky_tb.v

`timescale 1ns/1ns
module blinky_tb;

   parameter clk_freq_hz = 50_000;
   parameter pulses = 5;
   localparam clk_half_period = 1000_000_000/clk_freq_hz/2;

   reg clk = 1'b1;

   always #clk_half_period clk <= !clk;


   wire led;

   vlog_tb_utils vtu();

   blinky
     #(.clk_freq_hz (clk_freq_hz))
   dut
     (.clk (clk),
      .q   (led));

   integer i;
   time last_edge = 0;

   initial begin
      @(posedge clk);
      @(led);
      last_edge = $time;
      for (i=0; i<pulses;i=i+1) begin
	 @(led);
	 if (($time-last_edge) != 1_000_000_000) begin
	    $display("Error! Length of pulse was %0d ns", $time-last_edge);
	    $finish;
	 end else
	   $display("Pulse %0d/%0d OK!", i+1, pulses);
	 last_edge = $time;
      end
      $display("Testbench finished OK");
      $finish;
   end

endmodule