import java.util.;
import java.lang.;
import java.io.*;
/* Name of the class has to be “Main” only if the class is public. */
class Codechef
{
public static void main (String[] args) throws java.lang.Exception
{
// your code goes here
Scanner sc = new Scanner(System.in);
int test = sc.nextInt();
while(test>0)
{
int n = sc.nextInt();
int a[] = new int[n];
for(int i=0;i<n;i++)
{
a[i]=sc.nextInt();
}
Arrays.sort(a);
int min1 = a[0] ;
int min2 = 0;
for(int i=1;i<n;i++)
{
if(a[i]==min1)
{
continue;
}
else
{
min2 = a[i];
break;
}
}
System.out.println(min2-min1);
}
test--;
}
}