#include <bits/stdc++.h>
using namespace std;
template <typename TH>
void _dbg(const char* sdbg, TH h) {
  cerr << sdbg << "=" << h << "\n";
}
template <typename TH, typename... TA>
void _dbg(const char* sdbg, TH h, TA... t) {
  while (*sdbg != ',') {
    cerr << *sdbg++;
  }
  cerr << "=" << h << ",";
  _dbg(sdbg + 1, t...);
}
template <class C>
void mini(C& a4, C b4) {
  a4 = min(a4, b4);
}
template <class C>
void maxi(C& a4, C b4) {
  a4 = max(a4, b4);
}
template <class T1, class T2>
ostream& operator<<(ostream& out, pair<T1, T2> pair) {
  return out << "(" << pair.first << ", " << pair.second << ")";
}
template <class A, class B, class C>
struct Triple {
  A first;
  B second;
  C third;
  bool operator<(const Triple& t) const {
    if (first != t.first) return first < t.first;
    if (second != t.second) return second < t.second;
    return third < t.third;
  }
};
template <class T>
void ResizeVec(T&, vector<long long>) {}
template <class T>
void ResizeVec(vector<T>& vec, vector<long long> sz) {
  vec.resize(sz[0]);
  sz.erase(sz.begin());
  if (sz.empty()) {
    return;
  }
  for (T& v : vec) {
    ResizeVec(v, sz);
  }
}
template <class A, class B, class C>
ostream& operator<<(ostream& out, Triple<A, B, C> t) {
  return out << "(" << t.first << ", " << t.second << ", " << t.third << ")";
}
template <class T>
ostream& operator<<(ostream& out, vector<T> vec) {
  out << "(";
  for (auto& v : vec) out << v << ", ";
  return out << ")";
}
template <class T>
ostream& operator<<(ostream& out, set<T> vec) {
  out << "(";
  for (auto& v : vec) out << v << ", ";
  return out << ")";
}
template <class L, class R>
ostream& operator<<(ostream& out, map<L, R> vec) {
  out << "(";
  for (auto& v : vec) out << v << ", ";
  return out << ")";
}
const long long N = 1e6 + 22;
const long long L = 20;
const long long P = 1e9 + 7;
long long spow(long long a, long long b) {
  long long r = 1;
  while (b) {
    if (b % 2) {
      r = r * a % P;
    }
    a = a * a % P;
    b /= 2;
  }
  return r;
}
long long cnt[N];
struct Sol {
  void Test() {
    long long n, p;
    cin >> n >> p;
    set<long long> ls;
    for (long long i = (1); i <= (n); ++i) {
      long long k;
      cin >> k;
      cnt[k]++;
      ls.insert(k);
    }
    set<long long> or_ls = ls;
    if (p == 1) {
      cout << n % 2 << "\n";
      for (auto l : or_ls) {
        cnt[l] = 0;
      }
      return;
    }
    while (1) {
      if (ls.empty()) {
        for (auto l : or_ls) {
          cnt[l] = 0;
        }
        cout << "0\n";
        return;
      }
      auto it = prev(ls.end());
      long long val = *it;
      (val, cnt[val]);
      if (cnt[*it] % 2 == 0) {
        cnt[*it] = 0;
        ls.erase(it);
      } else {
        cnt[val] = 1;
        long long need = 1;
        for (long long i = (val - 1); i >= (-1); --i) {
          need *= p;
          if (need > n || i == -1) {
            long long res = spow(p, val);
            long long to_sub = 0;
            (ls);
            for (auto l : ls) {
              if (l < val) {
                to_sub = (to_sub + cnt[l] * spow(p, l)) % P;
              }
            }
            (res, to_sub);
            for (auto l : or_ls) {
              cnt[l] = 0;
            }
            cout << (res - to_sub + P) % P << "\n";
            return;
          } else {
            long long here = min(need, cnt[i]);
            need -= here;
            (here, i, val, need);
            if (need == 0) {
              cnt[i] -= here;
              for (long long j = (i + 1); j <= (val); ++j) {
                ls.erase(j);
                cnt[j] = 0;
              }
              break;
            }
          }
        }
      }
    }
  }
};
int32_t main() {
  ios_base::sync_with_stdio(0);
  cout << fixed << setprecision(10);
  if (0) cout << fixed << setprecision(10);
  cin.tie(0);
  long long t;
  cin >> t;
  for (long long i = (1); i <= (t); ++i) {
    Sol sol;
    sol.Test();
  }
  return 0;
}
