#include<cstdio>
#include<cstdlib>
#include<cstring>
using namespace std;
int main()
{
    int t,n,a[500];
    scanf("%d",&t);
    int i,j;
    int t1,t2;
    while(t--)
    {
        t1=0;
        scanf("%d",&n);
        t2=n*(n-1);
        memset(a,0,sizeof(a));
        for(i=0;i<n;i++)
            scanf("%d",&a[i]);
        for(i=0;i<n;i++)
            for(j=0;j<n;j++)
            {
                if(i==j)
                    continue;
                if(a[i]>a[j])
                    t1++;
            }
        double a,b,ans;
        a=(double)t1;
        b=(double)t2;
        ans=a/b;
        if(ans==-0.0)
            ans=0.0;
        printf("%.6lf\n",ans);
    }
    return 0;
}