#include <bits/stdc++.h>
using namespace std;
int main() {
  long long t;
  cin >> t;
  while (t--) {
    long long n;
    cin >> n;
    long long a[n + 1];
    for (long long i = 0; i < n; i++) cin >> a[i];
    sort(a, a + n);
    long long diff = INT_MAX;
    for (long long i = 0; i < n - 1; i++) {
      diff = min(a[i + 1] - a[i], diff);
    }
    cout << diff << endl;
  }
}
