#include <iostream>
#include <vector>
#include <algorithm>
#include <climits>
using namespace std;

/* brute force algorithm */
int min_diff1(vector<int>& arr)
{
    int min_diff = INT_MAX;
    int i,j;
    for( i = 0; i < arr.size()-1; i++ )
    {
        for( j = i+1; j < arr.size(); j++ )
        {
            min_diff = min(min_diff, abs(arr[i]-arr[j]));
        }
    }
    return min_diff;
}

int min_diff(vector<int>& arr)
{
    sort( arr.begin(), arr.end() );
    int min_diff = INT_MAX;
    for( i = 0; i < n-1; i++ )
    {
      min_diff = min(min_diff, abs(arr[i]-arr[i+1]));
    }
    return min_diff;
}

int main() {
    int t;
    cin >> t;
    while( t-- )
    {
        int n;
        cin >> n;
        vector<int> arr(n);
        int i;
        for( i = 0; i < n; i++ )
        {
            cin >> arr[i];
        }
        cout << min_diff(arr) << endl;
    }
    return 0;
}