#include<bits/stdc++.h>
#define N 100005
#define re 
#define ll long long
using namespace std;
int n,m,K,q,T;
inline void Rd(int &res){
    re char c;res=0;
    while(c=getchar(),c<48);
    do res=(res<<3)+(res<<1)+(c^48);
    while(c=getchar(),c>47);
}
double p[N];
int main(){
    Rd(T);
    while(T--){
        Rd(n);
        for(int i=1;i<=n;i++)scanf("%lf",&p[i]);

        sort(p+1,p+n+1);

        if(p[n]>0.5-(1e-8)){
            printf("%.10lf\n",p[n]);
            continue;
        }

        double p0=1.0,p1=0.0;

        for(int i=n;i>=1;i--){
            double p01=p0*(1.0-p[i]);

            double p11=p1*(1.0-p[i]) + p0*p[i] ;

            if(p11>p1)p1=p11,p0=p01; 

        }

        printf("%.10lf\n",p1);


    }
    

    return 0;
}