#include <bits/stdc++.h>
using namespace std;
int main() {
  int t;
  cin >> t;
  while (t--) {
    int n;
    cin >> n;
    int a[n];
    for (int i = 0; i < n; i++) {
      cin >> a[i];
    }
    sort(a, a + n);
    vector<int> v;
    for (int i = 0; i < n - 1; i++) {
      v.push_back(a[i + 1] - a[i]);
    }
    int min = *min_element(v.begin(), v.end());
    cout << min << endl;
  }
}
