#include <bits/stdc++.h>
 
using namespace std;
 
const int MaxN = 1e5 + 10;
 
int n, a[MaxN], who[MaxN];
double b[MaxN], upb[MaxN][2];
bool can;
vector < int > g[MaxN];

int getWho(int v) {
	return who[v] == v ? v : who[v] = getWho(who[v]);
}
 
void dfsUp(int v, int p) {
	upb[v][1] = upb[v][0] = -1e+40;
	vector < double > chld, rchld;
	for (auto to : g[v]) {
		if (to == p) {
			continue;
		}
		dfsUp(to, v);
		if (upb[to][0] < 0) {
			chld.push_back(upb[to][1]);
		} else {
			rchld.push_back(upb[to][1]);
		}
	}
	sort(rchld.rbegin(), rchld.rend());
	if ((int)chld.size() >= 3) {
		can = false;
		return;
	}
	if ((int)chld.size() == 2) {
		if (chld[1] + chld[0] + b[v] < 0) {
			can = false;
			return;
		}
		upb[v][0] = chld[1] + chld[0] + b[v];
		upb[v][1] = 0;
		return;
	} 
	if ((int)chld.size() == 1) {
		upb[v][0] = b[v] + chld[0] + (rchld.size() > 0 ? max(0.0, rchld[0]) : 0.0);
		upb[v][1] = b[v] + chld[0];
	}
	if ((int)chld.size() == 0) { 
		upb[v][1] = max(upb[v][1], b[v] + (rchld.size() > 0 ? max(0.0, rchld[0]) : 0));
		upb[v][0] = b[v];
		upb[v][0] += (rchld.size() > 0 ? max(0.0, rchld[0]) : 0);
		upb[v][0] += (rchld.size() > 1 ? max(0.0, rchld[1]) : 0);
	}
	if (upb[v][0] < upb[v][1]) {
		upb[v][0] = upb[v][1];
	}
	if (p == 0) {
		can &= (upb[v][0] >= 0);
	}
}
  
bool check(double x) {
	for (int i = 1; i <= n; ++i) {
		b[i] = a[i] - x;
	}
	can = true;
	srand(time(NULL));
	dfsUp(rand() % n + 1, 0);
	return can;
}
 
void solve() {
	scanf("%d", &n);
	assert (1 <= n && n <= 100000);
	int maxA = 0;
	for (int i = 1; i <= n; ++i) {
		scanf("%d", &a[i]);
		assert (1 <= a[i] && a[i] <= 100000);
		maxA = max(maxA, a[i]);
		who[i] = i;
	}
	for (int i = 1; i < n; ++i) {
		int x, y;
		scanf("%d%d", &x, &y);
		assert (1 <= x && x <= n);
		assert (1 <= y && y <= n);
		assert (getWho(x) != getWho(y));
		who[getWho(x)] = getWho(y);
		g[x].push_back(y);
		g[y].push_back(x);
	}
	for (int i = 1; i <= n; ++i) {
		assert (getWho(i) == getWho(1));
	}
	double l = 1e-6, r = maxA;
	for (int it = 0; it < 60; ++it) {
		double m = (l + r) / 2;
//		cerr << ' ' << l << ' ' << r << '\n';
		if (check(m)) {
			l = m;
		} else {
			r = m;
		}
	}
	for (int i = 1; i <= n; ++i) {
		g[i].clear();
	}
	printf("%.9lf\n", (l + r) / 2.0);
}
 
int main() {
//	freopen("input.txt", "r", stdin);
	int t;
	scanf("%d", &t);
	assert (1 <= t && t <= 20);
	while (t --> 0) {
		solve();
	}
 
	return 0;
}