#include <bits/stdc++.h>
using namespace std;
#pragma GCC optimize("-Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,sse4.2,popcnt,abm,mmx,avx2,tune=native")
#pragma GCC optimize("-ffast-math")
#pragma GCC optimize("-funroll-loops")
#pragma GCC optimize("-funroll-all-loops,-fpeel-loops,-funswitch-loops")
#define IO ios_base::sync_with_stdio(0), cin.tie(0), cout.tie(0);
const long long MOD = 1e9 + 7, OO = 1e18;
const double PI = acos(-1);
const int N = 1e3 + 5;
const int dx[4] = {0, 0, 1, -1};
const int dy[4] = {1, -1, 0, 0};

long long t, n, h, a[N], l, r, md;

bool ok(long long k)
{
    long long sm = 0;
    for (int i = 1; i < n; i++)
    {
        sm += min(a[i + 1] - a[i], k);
    }
    sm += k;

    return sm >= h;
}

int main()
{
    IO
    cin >> t;
    while (t--)
    {
        cin >> n >> h;
        for (int i = 1; i <= n; i++)
        {
            cin >> a[i];
        }
        l = 1, r = 1e18;
        while (l < r)
        {
            md = (l + r) / 2;
            if (ok(md))r = md;
            else l = md + 1;
        }
        cout << l << '\n';
    }
    return 0;
}