#include<cstdio>

#include<cstring>

#include<algorithm>

using namespace std;

#define lson rt<<1,l,m

#define rson rt<<1|1,m+1,r

const double EPS = 0.0000001;

int T;

int n,a[60010],last[60010],now[60010];

double minv[60010<<2];

double delta[60010<<2];

void pushdown(int rt)

{

    if(delta[rt])

      {

        delta[rt<<1]+=delta[rt];

        delta[rt<<1|1]+=delta[rt];

        minv[rt<<1]+=delta[rt];

        minv[rt<<1|1]+=delta[rt];

        delta[rt]=0;

      }

}

void update(int ql,int qr,double v,int rt,int l,int r)

{

    if(ql<=l&&r<=qr)

      {

        delta[rt]+=v;

        minv[rt]+=v;

        return;

      }

    pushdown(rt);

    int m=(l+r)>>1;

    if(ql<=m) update(ql,qr,v,lson);

    if(m<qr) update(ql,qr,v,rson);

    minv[rt]=min(minv[rt<<1],minv[rt<<1|1]);

}

double query(int ql,int qr,int rt,int l,int r)

{

    if(ql<=l&&r<=qr)

      return minv[rt];

    pushdown(rt);

    int m=(l+r)>>1;

    double res=2147483647.0;

    if(ql<=m) res=min(res,query(ql,qr,lson));

    if(m<qr) res=min(res,query(ql,qr,rson));

    return res;

}

bool check(double ratio){

	memset(minv,0,sizeof(minv));

	memset(delta,0,sizeof(delta));

	for(int i=1;i<=n;++i){

		update(i,i,ratio*(double)i,1,1,n);

	}

	for(int i=1;i<=n;++i){

		update(last[i]+1,i,1.0,1,1,n);

		if(query(1,i,1,1,n)-ratio*(double)(i+1)<EPS){

			return 1;

		}

	}

	return 0;

}

int main(){

	scanf("%d",&T);

	for(;T;--T){

		memset(now,0,sizeof(now));

		scanf("%d",&n);

		for(int i=1;i<=n;++i){

			scanf("%d",&a[i]);

		}

		for(int i=1;i<=n;++i){

			last[i]=now[a[i]];

			now[a[i]]=i;

		}

		double l=0.0,r=1.0;

		while(r-l>EPS){

			double mid=(l+r)*0.5;

			if(check(mid)){

				r=mid;

			}

			else{

				l=mid+EPS;

			}

		}

		printf("%.10lf\n",l);

	}

	return 0;

}