https://codeforces.com/contest/1734/problem/A

#include <bits/stdc++.h>
#define ll long long
#define MOD 1000000007
using namespace std;

const int inf = 1e9;

void solve() {
    int N; cin >> N;
    vector<int> A(N);
    for(int i = 0; i < N; i++) {
        cin >> A[i];
    }
    sort(A.begin(), A.end());
    int ans = inf;
    for(int i = 1; i < N - 1; i++) {
        ans = min(ans, A[i + 1] - A[i - 1]);
    }
    cout << ans << '\n';
}

int main() {
    ios::sync_with_stdio(0);
    cin.tie(0);
#ifdef LOCAL
    freopen("input.txt", "r", stdin);
    freopen("output.txt", "w", stdout);
#endif
    int test_cases = 1;
    cin >> test_cases;
    for(int test_case = 1; test_case <= test_cases; test_case++) {
        // cout << "Case #" << test_case << ": ";
        solve();
    }
    return 0;
}