//5114 - Christmas Play
//Live Archive

/*
Ordene os números e pegue a menor diferença entre Soldier[i] e Soldier[i+k] para todo i tal que i+k < n
*/

#include <cstdio>
#include <cstdlib>
#include <string>
#include <cmath>
#include <cstring>
#include <algorithm>
#include <utility>
#include <queue>
#include <stack>
#include <vector>
#include <map>
#include <iostream>

#define ln printf("\n")

using namespace std;

const int inf = 0x7f7f7f7f;
const double pi=acos(-1.0);
const double eps = 1e-8;

int n, k;
int r[20200];

bool read(){
	//if() return false;

	scanf("%d%d", &n, &k);

	for(int i = 0; i < n; i++){
		scanf("%d", &r[i]);
	}

	return true;
}

void process(){
	sort(r, r+n);

	int res = 2000000000;

	for(int i = 0; i+k-1 < n; i++){
		res = min(res, abs(r[i]-r[i+k-1]));
	}

	printf("%d\n", res);


}

int main(){
	//freopen("in", "r", stdin);
	int cases; scanf("%d", &cases);

	while(cases-- && /**/ read()){
		process();
	}

	//while(1);

	return 0;
}