import java.io.FileInputStream;
import java.util.*;

public class Main {
    public static void main(String[] args) throws Exception  {
        // TODO Auto-generated method stub
        Scanner sc = new Scanner(System.in);
        //Scanner sc = new Scanner(new FileInputStream("input.txt"));
        int cases = sc.nextInt();

        for(int i=0; i<cases; i++){
            int N=sc.nextInt();
            double[][] arr=new double[N][N];
            int tempN=sc.nextInt();
            for(int j=0; j<tempN; j++){
                int temp1=sc.nextInt();
                int temp2=sc.nextInt();
                double temp3=sc.nextDouble();
                arr[temp1][temp2]=temp3;
            }
            double[] distance=new double[N];
            distance[0]=1.0;
            for(int j=1; j<N; j++){
                distance[j]=999999999.9;
            }
            int count=0;
            int[] check=new int[N];
            check[0]=1;
            int level=1;
            while(level!=N){
                double min=99999999.9;
                int index=0;
                for(int j=0; j<N; j++){
                    if(count==j||arr[count][j]==0)continue;
                    if(distance[j]>distance[count]*arr[count][j])
                        distance[j]=distance[count]*arr[count][j];
                    if(check[j]!=1&&min>distance[j])index=j;
                }
                check[index]=1;
                count=index;
                level++;
            }
            System.out.printf("%.10f\n",distance[N-1]);
        }    
    }


}