#include <bits/stdc++.h>
using namespace std;

#define ff   first
#define ss   second
#define pb   push_back

typedef long long  ll;
typedef pair<ll,ll>  pii;

const ll N = 4e5 + 10;
const ll mod = 1e9 + 7;
const ll oo = 1e18;


int main() {
  ios_base::sync_with_stdio(0);
  cin.tie(0);

  #ifdef LOCAL
  freopen("input.txt","r",stdin);
  #endif // LOCAL

  int t; cin >> t;
  while (t--) {

    int n,m; cin >> n >> m;
    vector <int> a(n), b(m);
    for (auto &e : a) cin >> e;
    for (auto &e : b) cin >> e;

    sort (a.begin(), a.end());
    sort (b.begin(), b.end());

    int can = 1;
    if (m > n) can = 0;
    if (can == 0) {
      cout << -1 << '\n';
      continue;
    }

    ll sum = 0, fa = a[n - m], fb = b[0];

    vector <int> ty2;

    for (int i = n - 1, j = m - 1; j >= 0; --i, --j) {
      if (a[i] > b[j]) can = 0;
      else {
        if (sum + b[j] - a[i] > n - m) {
          can = 0;
          break;
        }
        for (int k = a[i]; k < b[j]; ++k) ty2.pb(k);
        sum += b[j] - a[i];
      }
    }

    if (can == 0) {
      cout << -1 << '\n';
      continue;
    }

    vector <int> ans, ty1;
    multiset <int> curr;
    for (auto &e : a) curr.insert(e);

    while (1) {
      int be = *curr.begin();
      if (be == fa) break;
      ty1.pb(be);
      curr.erase(curr.lower_bound(be));
      curr.insert(be + 1);
      be = *curr.begin();
      curr.erase(curr.lower_bound(be));
    }
    for (int i = 0; i < sum && curr.size() > m; ++i) {
      int be = *curr.begin();
      curr.erase(curr.lower_bound(be));
    }

    int szty1 = ty1.size(), szty2 = ty2.size();
    int sz = min(szty1, (n - m) - szty2);
    for (int i = 0; i < sz; ++i) ans.pb(ty1[i]);
    for (auto &e : ty2) ans.pb(e);

    for (int i = n - 1, j = m - 1; j >= 0; --i, --j) {
      curr.erase(curr.lower_bound(a[i]));
      curr.insert(b[j]);
    }

    while (1) {
      int be = *curr.begin();
      if (be == fb) break;
      ans.pb(be);
      curr.erase(curr.lower_bound(be));
      curr.insert(be + 1);
      be = *curr.begin();
      curr.erase(curr.lower_bound(be));
    }

    if (curr.size() > m) can = 0;

    if (can) {
      cout << n - m << '\n';
      assert(ans.size() == n - m);
      for (auto &e : ans) cout << e << ' ';
      if (n - m > 0)
        cout << '\n';
    }
    else cout << -1 << '\n';

  }

  return 0;
}