#include 
     
      #include 
      
       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;}