`timescale 1ns / 1ps

module tb_alu ();
    reg  [31:0] in_a;
    reg  [31:0] in_b;
    reg  [2:0]  op_code;
    wire [31:0] out;

    alu alu (
        .in_a(in_a),
        .in_b(in_b),
        .op_code(op_code),
        .out(out)
    );

    initial begin
        $monitor("time=%3d, in_a=%d, in_b=%d, ctrl=%b, q=%d \n",
                    $time, in_a, in_b, op_code, out);

        in_a = 1'b0;
        in_b = 1'b0;
        op_code = 3'b000;
        #20
        if (out !== 0) $display("[FAILED] output should be 0");
        in_a = 1'b1;
        #20
        if (out !== 1) $display("[FAILED] output should be 1");
        in_b = 1'b1;
        #20
        if (out !== 2) $display("[FAILED] output should be 2");
        op_code = 3'b001;
        #20
        if (out !== 2) $display("[FAILED] output should be 2");
    end

endmodule : tb_alu