#include <stdio.h>
#include <algorithm>
using namespace std;
#define gc getchar_unlocked
inline int getn(){
int n=0, c=gc();
while(c < '0' || c > '9') c = gc();
while(c >= '0' && c <= '9')
n = (n<<3) + (n<<1) + c - '0', c = gc();
return n;
}
bool waytosort(int i,int j){
return i<j;
}
int main()
{
int tc,i;
long long int s[5000],diff;
tc=getn();
while(tc--){
long long int mindiff=1000000000;
int n;
n=getn();
for(i=0;i<n;i++){
s[i]=getn();
}
sort(s,s+n,waytosort);
for(i=1;i<n;i++){
diff=s[i]-s[i-1];
if(diff<mindiff)
mindiff=diff;
}
printf("%lld\n",mindiff);
}
}
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