#if __INCLUDE_LEVEL__ == 0

#include __BASE_FILE__

namespace {

void solve() {
  int n, m;
  scan(n, m);
  vector<int> a(n);
  scan(a);
  vector<int> b(m);
  scan(b);
  ranges::sort(a);
  ranges::sort(b);

  auto a_rev = a | views::reverse;
  auto b_rev = b | views::reverse;

  int64_t c = 0;
  for (int i : rep(m)) {
    if (b_rev[i] < a_rev[i]) {
      print(-1);
      return;
    }
    c += b_rev[i] - a_rev[i];
  }
  if (n - m < c) {
    print(-1);
    return;
  }

  auto ms = ALL(multiset, a);
  vector<int> ans;
  ans.reserve(n - m);

  auto op = [&](int x) -> bool {
    if (ms.find(x) == ms.end()) {
      return false;
    }
    ms.erase(ms.find(x));
    ms.insert(x + 1);
    ms.erase(ms.begin());
    ans.push_back(x);
    return true;
  };

  for (int _ = n - m - c; _--;) {
    int x = *ms.begin();
    op(x);
  }

  {
    auto na = a | views::drop(n - m);
    int l = 0;
    while (true) {
      while (l < m && na[l] == b[l]) {
        ++l;
      }
      if (l == m) {
        break;
      }
      assert(na[l] < b[l]);
      int r = l + 1;
      while (r < m && na[l] == na[r]) {
        ++r;
      }
      for (int i : rep(l, r)) {
        if (!op(na[i])) {
          print(-1);
          return;
        }
        ++na[i];
      }
    }
  }

  if (ALL(vector, ms) != b) {
    print(-1);
    return;
  }

  assert(len(ans) == n - m);
  print(n - m);
  print(ans);
}

}  // namespace

int main() {
  ios::sync_with_stdio(false);
  cin.tie(nullptr);

  int t;
  scan(t);
  while (t--) {
    solve();
  }
}

#else  // __INCLUDE_LEVEL__

#include <bits/stdc++.h>

using namespace std;

#define ALL(f, r, ...) \
  [&](auto&& _) { return f(begin(_), end(_), ##__VA_ARGS__); }(r)

namespace std {

template <class T1, class T2>
istream& operator>>(istream& is, pair<T1, T2>& p) {
  return is >> p.first >> p.second;
}

template <class... Ts>
istream& operator>>(istream& is, tuple<Ts...>& t) {
  return apply([&is](auto&... xs) -> istream& { return (is >> ... >> xs); }, t);
}

template <class R, enable_if_t<!is_convertible_v<R, string>>* = nullptr>
auto operator>>(istream& is, R&& r) -> decltype(is >> *begin(r)) {
  for (auto&& e : r) {
    is >> e;
  }
  return is;
}

template <class T1, class T2>
ostream& operator<<(ostream& os, const pair<T1, T2>& p) {
  return os << p.first << ' ' << p.second;
}

template <class... Ts>
ostream& operator<<(ostream& os, const tuple<Ts...>& t) {
  auto f = [&os](const auto&... xs) -> ostream& {
    [[maybe_unused]] auto sep = "";
    ((os << exchange(sep, " ") << xs), ...);
    return os;
  };
  return apply(f, t);
}

template <class R, enable_if_t<!is_convertible_v<R, string_view>>* = nullptr>
auto operator<<(ostream& os, R&& r) -> decltype(os << *begin(r)) {
  auto sep = "";
  for (auto&& e : r) {
    os << exchange(sep, " ") << e;
  }
  return os;
}

}  // namespace std

void scan(auto&&... xs) { (cin >> ... >> xs); }
void print(auto&&... xs) { cout << tie(xs...) << '\n'; }

inline auto rep(int l, int r) { return views::iota(min(l, r), r); }
inline auto rep(int n) { return rep(0, n); }
inline auto rep1(int l, int r) { return rep(l, r + 1); }
inline auto rep1(int n) { return rep(1, n + 1); }
inline auto per(int l, int r) { return rep(l, r) | views::reverse; }
inline auto per(int n) { return per(0, n); }
inline auto per1(int l, int r) { return per(l, r + 1); }
inline auto per1(int n) { return per(1, n + 1); }

inline auto len = ranges::ssize;

#endif  // __INCLUDE_LEVEL__