#include<iostream>
#include<fstream>
#include<iomanip>
#include<stdio.h>
#include<cstdio>
#include<math.h>
#include<cmath>
#include<algorithm>
#include<string>
#include<cstring>
#include<string.h>
#include<vector>
#include<stack>
#include<queue>
#include<map>
#include<set>
#include<cstdlib>
#include<stdlib.h>
#include<ctime>
#include<time.h>
using namespace std;
#define LL long long
const int N=1e5+5;
const int INF=0x3f3f3f3f;
int T,n,m,cnt,num;
double ans;
int xx[1100],yy[1100];
int fa[1100];
struct node{
	int x,y;
	double z;
}edg[6001000];
int find(int x){
	return fa[x]==x?x:fa[x]=find(fa[x]);
}
bool cmp(node a,node b){
	return a.z<b.z;
}
void init(){
	num=1;
	for(int i=1;i<=m;i++){
		for(int j=1;j<=m;j++){
			if(i==j){
				continue;
			}
			edg[num].x=i;
			edg[num].y=j;
			edg[num].z=sqrt(1.0*pow(xx[i]-xx[j],2)+pow(yy[i]-yy[j],2));
			num++;
		}
	}
	num--;
	sort(edg+1,edg+num+1,cmp);
	for(int i=1;i<=m;i++){
		fa[i]=i;
	}
}
void kruskal(){
	int xx,yy;
	for(int i=1;i<=num;i++){
		xx=find(edg[i].x);
		yy=find(edg[i].y);
		if(xx!=yy){
			cnt++;
			fa[xx]=yy;
			ans=edg[i].z;
		}
		if(cnt==m-n){
			break;
		}
	}
}
int main(){
	/*
	freopen(".in","r",stdin);
	freopen(".out","w",stdout);
	*/
	cin>>T;
	while(T--){
		memset(edg,0,sizeof(edg));
		cin>>n>>m;
		cnt=0;
		for(int i=1;i<=m;i++){
			cin>>xx[i]>>yy[i];
		}
		init();
		kruskal();
		cout<<fixed<<setprecision(2)<<ans<<endl;
	}
	return 0;
}