/**
* BRACKETS2
*
* @author Seungchul Lee
* @solved 2016. 10. 03
*
* http://algospot.com/judge/problem/read/FESTIVAL
*/
#define _CRT_SECURE_NO_WARNINGS
#include <iostream>
#include <cstring>
#include <cstdio>
#include <algorithm>
#include <string>
#include <vector>
#include <list>
#include <stack>
using namespace std;

#define INF 987654321

namespace FESTIVAL {

    int N;
    int L;
    vector<double> costs;

    vector<double> movingAverage2(const vector<double>&A, int L) {
        int N = A.size();
        vector<double> ret;
        double partialSum = 0;
        if (L == N) {
            for (int i = 0; i < L; ++i) {
                partialSum += A[i];
            }
            ret.push_back(partialSum / N);
            return ret;
        }

        for (L; L < N ; ++L) {
            for (int i = 0; i < L - 1; ++i) {
                partialSum += A[i];
            }
            for (int i = L - 1; i < N; ++i) {
                partialSum += A[i];
                ret.push_back(partialSum / L);
                partialSum -= A[i - L + 1];
            }
            partialSum = 0;
        }


        return ret;
    }

    int do_main(int argc, const char *argv[]) {
        freopen("input.txt", "r", stdin);
        int TC;
        int cnt = 0;

        cin >> TC;

        while (TC--) {
            cin >> N;
            cin >> L;

            for (int i = 0; i < N; ++i) {
                double num = 0;
                cin >> num;
                costs.push_back(num);
            }

            vector<double> ans = movingAverage2(costs, L);
            double minVal = 987654321;
            while (!ans.empty()) {
                minVal = min(minVal, ans.back());
                ans.pop_back();
            }

            printf("%.12f\n", minVal);
            ans.clear();
        }

        return 0;
    }
}

#ifndef DRIVER

int main(int argc, const char *argv[]) {
    return FESTIVAL::do_main(argc, argv);
}

#endif