#include <stdio.h>

#include <string.h>

int main(int argc, char *argv[])

{

	int T,i,j,lineSum;

	int N,M;

	int x[505],y[505];

	int lineL [505][505] ;

	scanf("%d",&T);

	for(i = 0 ; i < T ;i++){

		lineSum = 0;

		scanf("%d %d",&N,&M); 

		memset (lineL,0,sizeof(lineL));

		memset (lineL,0,sizeof(x));

		memset (lineL,0,sizeof(y));

		for(j = 0 ; j < M ;j++){

			scanf("%d",&x[j]);

		}

		for(j = 0 ; j < M ;j++){

			scanf("%d",&y[j]);

		}

		for(j = 0 ; j < M ;j++){

			if(lineL[x[j]][y[j]] == 0 && lineL[y[j]][x[j]] == 0){

				lineSum ++;

				lineL[x[j]][y[j]]=lineL[y[j]][x[j]]=1;	

			}

		}

		printf("%.3f\n",lineSum/(N*1.0));

	} 

	return 0;

}