#include<stdio.h>
#include<assert.h>
#define REP(i,a,b) for(i=a;i<b;i++)
#define rep(i,n) REP(i,0,n)

void intSort(int d[],int s){int i=-1,j=s,k,t;if(s<=1)return;k=(d[0]+d[s-1])/2;for(;;){while(d[++i]<k);while(d[--j]>k);if(i>=j)break;t=d[i];d[i]=d[j];d[j]=t;}intSort(d,i);intSort(d+j+1,s-j-1);}

int main(){
  int T, N, S[5000];
  int i, res;

  assert( scanf("%d",&T)==1 );
  assert( 1<=T && T<=10 );
  while(T--){
    assert( scanf("%d",&N)==1 );
    assert( 2<=N && N<=5000 );
    rep(i,N) assert( scanf("%d",S+i)==1 ), assert( 1<=S[i] && S[i]<=1000000000 );
    intSort(S, N); /* sort such as S[0] <= S[1] <= S[2] <= ... */
    res = S[1] - S[0];
    REP(i,2,N) if(res > S[i]-S[i-1]) res = S[i]-S[i-1];
    printf("%d\n",res);
  }

  return 0;
}