#include <bits/stdc++.h>
using namespace std;
#define int long long




void solve() {
	int n, m;
	cin >> n >> m;
	vector<int>a(n + 1);
	vector<int>b(m + 1);
	for (int i = 1; i <= n; i++) {
		cin >> a[i];
	}
	for (int j = 1; j <= m; j++) {
		cin >> b[j];
	}
	sort(a.begin() + 1, a.end());
	sort(b.begin() + 1, b.end());
	int res = 0;
	for (int i = 1; i <= m; i++) {
		if (b[i] < a[i + n - m]) {
			cout << "-1" << endl;
			return;
		}
		if (b[i] > a[i + n - m]) {
			res += b[i] - a[i + n - m];
		}
	}
	priority_queue<int, vector<int>, greater<int>>q1, q2;
	for (int i = 1; i <= n - m; i++) {
		q1.push(a[i]);
	}
	for (int i = n - m + 1; i <= n; i++) {
		q2.push(a[i]);
	}
	vector<int>ans;
	while(q1.size() > res) {
        int now = q1.top();q1.pop();
        ans.push_back(now);
        if(now + 1 > q2.top()) {
            res--;
            if(res < 0) {
                cout << -1 << endl;
                return;
            }
            q1.push(q2.top());
            q2.pop();
            q2.push(now + 1);
            q1.pop();
        } else {
            q1.push(now + 1);
            q1.pop();
        }
    }
    int idx = 1;
    while(q2.size()) {
        int now = q2.top();
        if(now == b[idx]) {
            q2.pop();
            idx++;
        } else if(now > b[idx]) {
            cout << -1 << endl;
            return;
        } else {
            q2.pop();
            ans.push_back(now);
            q2.push(now + 1);
        }
    }
	cout << ans.size() << endl;
	for (int i = 0; i < ans.size(); i++) {
		cout << ans[i] << " ";
	}
	cout << endl;
	return;
}


signed main() {
	ios::sync_with_stdio(false);
	int tt = 1;
	cin >> tt;
	while (tt--) {
		solve();
	}
}