#include <bits/stdc++.h>
#define sz(x) ((int)(x).size())
#define all(x) begin(x), end(x)
#ifdef memset0
#define log(...) fprintf(stderr, __VA_ARGS__)
#else
#define endl '\n'
#define log(...) (void(0))
#endif
using namespace std;
using ll = long long;
using lf = long double;
using ull = unsigned long long;

const int N = 1e4 + 9;
int T, n;
double p[N];

int main() {
#ifdef memset0
  freopen("C.in", "r", stdin);
#endif
  cin.tie(0)->sync_with_stdio(0);
  cin >> T;
  while (T--) {
    cin >> n;
    for (int i = 1; i <= n; i++) {
      cin >> p[i];
    }
    sort(p + 1, p + n + 1);
    reverse(p + 1, p + n + 1);
    double ans = p[1], pre = 1 - p[1];
    for (int i = 2; i <= n; i++) {
      double cur = ans * (1 - p[i]) + pre * p[i];
      if (cur > ans) {
        ans = cur;
        pre *= 1 - p[i];
      } else {
        break;
      }
    }
    cout << fixed << setprecision(12) << ans << endl;
  }
}