#include <bits/stdc++.h>
#define int long long
using namespace std;
const int N = 4e5;
int a[N], b[N], c[N];
const int inf = 1e18;
void print(multiset<int> st)
{
    for (auto c : st)
    {
        cout << c << " ";
    }
    cout << endl;
}
void solve()
{
    int n, m;
    cin >> n >> m;
    for (int i = 1; i <= n; i++)
    {
        cin >> a[i];
    }
    for (int i = 1; i <= m; i++)
    {
        cin >> b[i];
    }
    if (m > n)
    {
        cout << -1 << endl;
        return;
    }
    sort(a + 1, a + 1 + n);
    sort(b + 1, b + 1 + m);
    int l = m, need = 0;
    vector<int> ans;
    for (int i = n; i >= n - m + 1; i--)
    {
        if (b[l] < a[i])
        {
            cout << -1 << endl;
            return;
        }
        need += b[l] - a[i];
        l--;
    }
    int shiji = n - m, cha = shiji - need;
    if (cha < 0)
    {
        cout << -1 << endl;
        return;
    }
    multiset<int> st, sc;
    for (int i = n; i >= n - m + 1; i--)
        st.insert(a[i]);
    for (int i = 1; i <= n; i++)
        sc.insert(a[i]);
    while (cha > 0 && !sc.empty())
    {
        auto u = *sc.begin();
        sc.erase(sc.begin());
        sc.insert(u + 1);
        ans.push_back(u);
        if (u + 1 > *st.begin())
        {
            st.erase(st.begin());
            need--;
            if (need < 0)
            {
                cout << -1 << endl;
                return;
            }
            st.insert(u + 1);
        }
        else
            cha--;
        sc.erase(sc.begin());
    }
    // print(sc);
    l = n - m + 1;
    int r = 1;
    while (!st.empty())
    {
        auto u = *st.begin();
        st.erase(st.begin());
        if (u == b[r])
        {
            r++;
            continue;
        }
        ans.push_back(u);
        st.insert(u + 1);
        sc.erase(sc.begin());
        sc.insert(u + 1);
    }
    cout << ans.size() << endl;
    for (auto c : ans)
    {
        cout << c << " ";
    }
    cout << endl;
}
signed main()
{
    ios::sync_with_stdio(false), cin.tie(0);
    int T = 1;
    cin >> T;
    while (T--)
        solve();
}