#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
#define X first
#define Y second
#define ALL(v) v.begin(), v.end()
#define pb push_back
#define SZ(a) ((int)a.size())

void solve() {
    int n, m;
    cin >> n >> m;
    vector<int> A(n), B(m);
    multiset<int> st;
    for (int i = 0; i < n; i++)
        cin >> A[i], st.insert(A[i]);
    for (int i = 0; i < m; i++)
        cin >> B[i];   
    sort(ALL(A), greater<int>());
    sort(ALL(B), greater<int>());
    A.resize(m);
    int quota = n - m;
    vector<int> v;
    for (int i = 0; i < m; i++)
        if (A[i] > B[i] || B[i] - A[i] > quota) {
            cout << -1 << "\n";
            return;
        }
        else {
            // cerr << A[i] << " " << B[i] << endl;
            for (int x = A[i]; x < B[i]; x++) {
                v.pb(x); 
                quota--;
            }
        }
    sort(ALL(v));
    // for (int i = 0; i < SZ(v); i++)
    //     cerr << v[i] << " \n"[i + 1 == SZ(v)];
    vector<int> tmp;
    for (int i = 0; i < quota; i++) {
        int x = *st.begin();
        st.erase(st.begin());
        st.insert(x + 1);
        st.erase(st.begin());
        tmp.pb(x);
        // cerr << "tmp " << x << endl;
    }
    for (int i = 0; i < SZ(v); i++) {
        if (st.find(v[i]) == st.end()) {
            cout << -1 << "\n";
            return;
        }
        st.erase(st.lower_bound(v[i]));
        st.insert(v[i] + 1);
        st.erase(st.begin());
    }
    vector<int> C;
    for (int x : st)
        C.pb(x);
    reverse(ALL(B));
    // for (int i = 0; i < SZ(C); i++)
    //     cerr << C[i] << " \n"[i + 1 == SZ(C)];
    if (B != C) {
        cout << -1 << "\n";
        return;
    }
    for (int x : v)
        tmp.pb(x);
    cout << n - m << "\n";
    for (int i = 0; i < n - m; i++)
        cout << tmp[i] << " \n"[i + 1 == n - m];
}

int main() {
    ios::sync_with_stdio(0), cin.tie(0);
    int T;
    cin >> T;
    while (T--)
        solve();
}