#include <bits/stdc++.h>

using i64 = long long;

void solve() {
    int n, m;
    std::cin >> n >> m;

    std::multiset<int> f1, f2;
    std::vector<int> b(m);
    for (int i = 0; i < n; i++) {
        int x;
        std::cin >> x;

        f1.emplace(x);
    }

    for (int i = 0; i < m; i++) {
        std::cin >> b[i];
    }

    i64 sum = 0;
    int cnt = m - 1;

    for (auto x : std::ranges::views::reverse(f1)) {
        if (cnt == -1) {
            break;
        }

        f2.emplace(x);
        if (x > b[cnt]) {
            std::cout << "-1\n";
            return;
        }

        sum += b[cnt--] - x;
    }

    if (sum > n - m) {
        std::cout << "-1\n";
        return;
    }

    cnt = n - m - sum;

    std::vector<int> ans;
    while (cnt) {
        int x = *f1.begin();
        f1.erase(f1.begin());
        f1.emplace(x + 1);
        f1.erase(f1.begin());

        ans.push_back(x);
        if (x + 1 > *f2.begin()) {
            f2.erase(f2.begin());
            f2.emplace(x + 1);

            sum -= 1;

            if (sum < 0) {
                std::cout << "-1\n";
                return;
            }
        } else {
            cnt -= 1;
        }
    }

    int r = m - 1;
    while (r != -1) {
        if (f1.empty() || b[r] < *f1.rbegin()) {
            std::cout << "-1\n";
            return;
        }

        while (*f1.rbegin() != b[r]) {
            if (f1.size() == 1) {
                std::cout << "-1\n";
                return;
            }
            int x = *f1.rbegin();
            ans.push_back(x);
            f1.erase(std::prev(f1.end()));
            f1.emplace(x + 1);
            f1.erase(f1.begin());
        }

        r--;
        f1.erase(std::prev(f1.end()));
    }

    if (int(f1.size()) != 0) {
        std::cout << "-1\n";
        return;
    }

    std::cout << int(ans.size()) << "\n";
    for (auto x : ans) {
        std::cout << x << " ";
    }
    std::cout << "\n";
}

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

    int t;
    std::cin >> t;

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

    return 0;
}