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

int n, m;

void solve()
{
    cin >> n >> m;
    multiset<int> ms1, ms2;
    for (int i = 1; i <= n; ++i)
    {
        int x;
        cin >> x;
        ms1.insert(x);
    }
    for (int i = 1; i <= m; ++i)
    {
        int x;
        cin >> x;
        ms2.insert(x);
    }

    ll need = 0;
    int lef = 2e9;
    multiset<int> ms;
    vector<pair<int, int>> suf;
    while (ms2.size())
    {
        if (*ms2.rbegin() < *ms1.rbegin())
        {
            cout << "-1\n";
            return;
        }
        need += *ms2.rbegin() - *ms1.rbegin();
        suf.emplace_back(*ms1.rbegin(), *ms2.rbegin());
        ms.insert(*ms1.rbegin());
        lef = min(lef, *ms2.rbegin());
        ms2.erase(prev(ms2.end()));
        ms1.erase(prev(ms1.end()));
    }
    if (ms1.size() < need)
    {
        cout << "-1\n";
        return;
    }

    vector<int> ans;
    while (ms1.size() > need)
    {
        int x = *ms1.begin();
        ms1.erase(ms1.begin());
        ms1.insert(x + 1);
        ans.push_back(x);
        if (*ms1.begin() > *ms.begin())
        {
            cout << "-1\n";
            return;
        }
        ms1.erase(ms1.begin());
    }

    reverse(suf.begin(), suf.end());
    vector<int> t;
    for (auto e : suf)
    {
        for (int i = e.first; i < e.second; ++i)
        {
            t.push_back(i);
        }
    }
    sort(t.begin(), t.end());
    for (auto e : t) ans.push_back(e);

    while (ms1.size())
    {
        if (*ms.begin() < lef)
        {
            int x = *ms.begin();
            ms.erase(ms.begin());
            ms.insert(x + 1);
        }
        if (*ms1.begin() > *ms.begin())
        {
            cout << "-1\n";
            return;
        }
        ms1.erase(ms1.begin());
    }
    cout << ans.size() << '\n';
    for (auto e : ans) cout << e << ' ';
    cout << '\n';
    return;
}

int main()
{
    ios::sync_with_stdio(0);
    cin.tie(0);
    cout.tie(0);
    int T = 1;
    cin >> T;
    while (T--) solve();
    return 0;
}