#include<bits/stdc++.h>
using namespace std;
const int mod=998244353;
const int maxn=3e5+5;
inline int read() {
	int x=0,f=1;
	char ch=getchar();
	while(ch<'0'||ch>'9') {if(ch=='-') f=-1;ch=getchar();}
	while(ch>='0'&&ch<='9') {x=(x<<1)+(x<<3)+(ch^48);ch=getchar();}
	return x*f;
}
typedef long long ll;
typedef long double lb;
ll now1,sum1,now2,sum2;
int T,n,a[maxn];
int main() {
	T=read();
	while(T--) {
		n=read();
		for(int i=1;i<=n;++i) a[i]=read();
		int now=1,flag=0,p=0;
		now1=sum1=now2=sum2=0;
		if(a[1]<a[2]) flag=1;
		lb ans=0.0;
		while(now<=n) {
			if(flag==0) {
				while(a[now]>a[now+1]&&now+1<=n) now1++,sum1+=a[now],now++;
				p=now,now++;
			}
			while(a[now]<a[now+1]&&now+1<=n) now2++,sum2+=a[now],now++;
			if(now+1==n||a[now]>a[now+1]) now2++,sum2+=a[now],now++;
			if(now1&&now2) {
				sum1-=a[p-1],now1--;
				sum2-=a[p+1],now2--;
				ll res=a[p]+a[p-1]+a[p+1];
				ans=max(ans,(lb)(sum1+sum2+res)/(lb)(now1+now2+3));
				ans=max(ans,(lb)(sum1+res)/(lb)(now1+3));
				ans=max(ans,(lb)(sum2+res)/(lb)(now2+3));
				//printf("%lld %lld %lld %lld %lld 3\n",sum1,res,sum2,now1,now2);
			}
			while(now<=n&&a[now]==a[now+1]) now++;
		}
		printf("%.15Lf\n",ans);
	}
	return 0;
}