#include <bits/stdc++.h>
using namespace std;
void fun() {}
long long int md = 1e9 + 7;
long long int __gcd(long long int a, long long int b) {
  if (b == 0) return a;
  return __gcd(b, a % b);
}
long long int poww(long long int a, long long int b, long long int md) {
  if (b < 0) return 0;
  if (a == 0) return 0;
  long long int res = 1;
  while (b) {
    if (b & 1) {
      res = (1ll * res * a) % md;
    }
    a = (1ll * a * a) % md;
    b >>= 1;
  }
  return res;
}
long long int poww(long long int a, long long int b) {
  if (b < 0) return 0;
  if (a == 0) return 0;
  long long int res = 1;
  while (b) {
    if (b & 1) {
      res = (1ll * res * a);
    }
    a = (1ll * a * a);
    b >>= 1;
  }
  return res;
}
void ainp(long long int arr[], long long int n) {
  for (long long int i = 1; i <= n; i++) cin >> arr[i];
}
void disp(long long int arr[], long long int n) {
  for (long long int i = 1; i <= n; i++) cout << arr[i] << " ";
  cout << "\n";
}
void dispv(vector<long long int> &v) {
  for (long long int i = 0; i < v.size(); i++) cout << v[i] << " ";
  cout << "\n";
}
long long int divide(long long int a, long long int b, long long int md) {
  long long int rr = a * (poww(b, md - 2, md));
  rr %= md;
  return rr;
}
signed main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  fun();
  long long int t;
  cin >> t;
  while (t--) {
    long long int n, k;
    cin >> n >> k;
    long long int a;
    map<long long int, long long int> mapp;
    for (long long int i = 1; i <= n; i++) {
      cin >> a;
      long long int md = a % k;
      long long int inc = (k - md) % k;
      mapp[inc]++;
    }
    long long int maxi = -1;
    for (auto i : mapp) {
      if (i.first == 0) continue;
      for (long long int j = 1; j < i.second; j++) mapp[i.first + j * k]++;
      mapp[i.first] = 1;
      maxi = max(maxi, i.first);
    }
    cout << maxi + 1 << "\n";
  }
  return 0;
}
