#include <bits/stdc++.h>
using namespace std;
int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);
  cout.tie(0);
  int t, n;
  cin >> t;
  while (t--) {
    cin >> n;
    int a[n];
    for (int i = 0; i < n; i++) cin >> a[i];
    sort(a, a + n);
    int lowdif = INT_MAX;
    for (int i = 1; i < n; i++) {
      if (a[i] - a[i - 1] < lowdif) lowdif = a[i] - a[i - 1];
    }
    cout << lowdif << "\n";
  }
  return 0;
}
