#include <cstdio>
int getint() {
    int r = 0, k = 1; char c = getchar();
    for (; c < '0' || c > '9'; c = getchar())if (c == '-') k = -1;
    for (; '0' <= c && c <= '9'; c = getchar()) r = r * 10 - '0' + c;
    return r * k;
}
int T,n,a[500];
int main () {
    T=getint();
    while (T--) {
        n = getint();
        for (int i = 1; i <= n; ++i) a[i] = getint();
        int cnt = 0, tot = 0;
        for (int i = 1; i <= n; ++i)
            for (int j = 1; j <= n; ++j) {
                if (i != j) {
                    ++tot;
                    if (a[i] > a[j]) ++cnt;
                }
            }
        printf("%.6lf\n", double(cnt) / double(tot));
    }
}