#include<stdio.h>
#include
#include
#include
#include
//#include
using namespace std;
int main()
{
int test_cases,length,len;
int p1,p2,count;
for(scanf("%d",&test_cases);test_cases--;){
count=0;
scanf("%d",&length);
int horse[length];
int len=length-1;
for(int i=0;i<length;i++)scanf("%d",&horse[i]);
sort(horse,horse+length);
int min1;
//while(p1>-1){
for(int i=0;i<len;i++)
for(int j=0;j<len;j++)
{if(j==i)
continue;
min1=min(abs(horse[i],horse[j]));
}
cout<<min1;
}
cin>>p2;
}