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

void solve() {
    ll n, m; std::cin >> n >> m;
    std::vector<ll> A(n + 1), B(m + 1);
    for(ll i = 1; i <= n; i++) {
        std::cin >> A[i];
    }
    for(ll i = 1; i <= m; i++) {
        std::cin >> B[i];
    }
    sort(A.begin() + 1, A.end());
    sort(B.begin() + 1, B.end());
    std::vector<ll> op;
    ll cnt = 0, flag = 1;
    for(ll i = n, j = m; j >= 1; i--) {
        if(A[i] > B[j]) {
            flag = 0;
            break;
        }
        cnt += B[j] - A[i];
        if(cnt > i - 1) {
            flag = 0;
            break;
        }
        for(int k = 0; k < B[j] - A[i]; k++) {
            op.push_back(A[i] + k);
        }
        j--;
    }
    if(!flag) {
        std::cout << -1 << '\n';
        return ;
    }
    std::priority_queue<ll, std::vector<ll>, std::greater<ll>> q;
    for(ll i = 1; i <= n - m - cnt; i++) {
        q.push(A[i]);
    }
    ll num = n - m - cnt;
    while(num > 0) {
        auto u = q.top(); q.pop();
        op.push_back(u);
        u += 1;
        if(u > B[1]) {
            std::cout << -1 << '\n';
            return ;
        }
        q.push(u);
        auto v = q.top(); q.pop();
        num--;
    }
    sort(op.begin(), op.end());
    std::cout << op.size() << '\n';
    for(int i = 0; i < op.size(); i++) {
        std::cout << op[i] << " \n"[i == op.size() - 1];
    }
}

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