#include <cstdio>
#include <cmath>
#include <cstring>
#include <algorithm>
#define inf 1e9
#define esp 1e-8
#define NN
#define LL long long
#define rep(i,s,t) for (int i=s;i<=t;i++)
#define red(i,t,s) for (int i=t;i>=s;i--)
using namespace std;
int n,m;

inline int read()
{
    int t=0,f=1;char ch=getchar();
    while(ch<'0'||ch>'9')f=(ch=='-')?-1:f,ch=getchar();
    while(ch>='0'&&ch<='9')t=t*10+ch-'0',ch=getchar();
    return t*f;
}
int a[1001];
int main()
{
//    freopen("1.in","r",stdin);//freopen("1.out","w",stdout);
    int T=read();
    rep(i,1,T)
    {
        int n=read();
        int num=0;
        rep(i,1,n)
            a[i]=read();
        rep(i,1,n)
            rep(j,1,n)
                if(i!=j)
                    if(a[i]>a[j])num++;
        printf("%.6lf\n",(double)num/(double)(n*(n-1)));
    }
    return 0;
}