#include <bits/stdc++.h>
using namespace std;
void input(int &x) {
  bool neg = false;
  register int c;
  x = 0;
  c = getchar();
  if (c == '-') {
    neg = true;
    c = getchar();
  }
  for (; (c > 47 && c < 58); c = getchar()) x = (x << 1) + (x << 3) + c - 48;
  if (neg) x *= -1;
}
int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    int arr[n];
    for (int i = 0; i < n; i++) {
      cin >> arr[i];
    }
    sort(arr, arr + n);
    int m = INT_MAX;
    for (int i = 1; i < n; i++) {
      m = min(m, abs(arr[i] - arr[i - 1]));
    }
    cout << m << endl;
  }
  return 0;
}
