#include <cmath>
#include <string>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <iostream>
#include <algorithm>


using namespace std;

bool cmp(int a, int b)
{
    return a>b;
}

double solve()
{
     int n, i, j;
     scanf("%d",&n);
     int a[500];
     for(i = 0; i<n; i++)
     {
          scanf("%d",&a[i]);
     }
     sort(a, a+n, cmp);

     double sum = n*(n-1);
     double cnt = 0;
     for(i = 0; i<n-1; i++)
     {
          for(j = i+1; j<n; j++)
          {
               if(a[i] > a[j])
                    cnt++;
          }
     }
     double t = cnt/sum;
     //printf("cnt = %d\n sum = %d\n",cnt,sum);
    //printf("t = %llf\n",t);
     return t;
}

int main (void)
{
     int t;
     scanf("%d",&t);
     while(t--)
     {
          double q = solve();
          printf("%0.6lf\n",q);
     }

    return 0 ;
}