#include <bits/stdc++.h>
using a2 = std::array<int, 2>;

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

    std::vector<int> output;

    std::vector<int> a(n + 1, 0), b(m + 1, 0);
    for (int i = 1; i <= n; i++) {
        std::cin >> a[i];
    }
    for (int i = 1; i <= m; i++) {
        std::cin >> b[i];
    }

    std::sort(a.begin() + 1, a.end());
    std::sort(b.begin() + 1, b.end());

    int asum = 0, bsum = 0;
    std::multiset<int> seqa1;
    std::multiset<int> seqa2;
    for (int i = n, j = m; j >= 1; i--, j--) {
        if (a[i] > b[j]) {
            std::cout << "-1\n";
            return;
        }
        asum += a[i], bsum += b[j];
        seqa2.insert(a[i]);
    }

    int more = n - m;
    int add = bsum - asum;

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

    for (int i = 1; i <= n - m; i++) {
        seqa1.insert(a[i]);
    }

    while (more - add > 0) {
        if (seqa1.empty()) {
            std::cout << "-1\n";
            return;
        }
        int now = *seqa1.begin();
        seqa1.erase(seqa1.begin());
        output.emplace_back(now);
        now++;
        if (seqa2.size() < m || *seqa2.begin() < now) {
            add--;
            seqa2.insert(now);
            seqa1.insert(*seqa2.begin());
            seqa2.erase(seqa2.begin());  
        } else {
            seqa1.insert(now);
        }
        if (seqa1.size()) seqa1.erase(seqa1.begin());
        else seqa2.erase(seqa2.begin());
        more--;
    }

    // std::cout << seqa1.size() << '\n';
    for (int i = 1; i <= m; i++) {
        int now = *seqa2.begin();
        seqa2.erase(seqa2.begin());
        if (now > b[i]) {
            std::cout << "-1\n";
            return;
        }
        while (now < b[i] && seqa1.size()) {
            output.emplace_back(now);
            now++;
            seqa1.erase(seqa1.begin());
        }
        // std::cout << seqa1.size() << '\n';
        if (now < b[i]) {
            std::cout << "-1\n";
            return;
        }
    }
    std::cout << output.size() << '\n';
    for (auto num : output) {
        std::cout << num << ' ';
    }
    std::cout << '\n';
}

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

    int T;
    std::cin >> T;
    while (T--) {
        solve();
    }
    return 0;
}