module tb;
    logic [6:0] opcode;
    logic alu_imm, alu_reg, load, store, branch, jump, illegal;
    integer legal = 0;
    string trace_file;
    opcode_decoder dut (.*);
    task automatic check_opcode(input logic [6:0] value, input logic [5:0] selected);
        opcode = value; #1;
        if ({jump, branch, store, load, alu_reg, alu_imm} != selected || illegal)
            $fatal(1, "FAIL task02 opcode=%h selected=%b illegal=%b", opcode, {jump, branch, store, load, alu_reg, alu_imm}, illegal);
        legal += 1;
    endtask
    initial begin
        if ($value$plusargs("trace=%s", trace_file)) begin $dumpfile(trace_file); $dumpvars(0, tb); end
        check_opcode(7'h13, 6'b000001); check_opcode(7'h33, 6'b000010); check_opcode(7'h03, 6'b000100);
        check_opcode(7'h23, 6'b001000); check_opcode(7'h63, 6'b010000); check_opcode(7'h6f, 6'b100000); check_opcode(7'h67, 6'b100000);
        opcode = 7'h7f; #1;
        if (!illegal || {jump, branch, store, load, alu_reg, alu_imm} != 0) $fatal(1, "FAIL task02 illegal default");
        $display("PASS task02 legal=%0d jump_opcodes=6f,67 illegal_7f=1", legal);
        $finish;
    end
endmodule