#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);
	map<int, int>mp;
	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());
	for (int i = 1; i <= n; i++) {
		mp[a[i]] = i;
	}
	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];
		}
	}
	if (res > n - m) {
		cout << "-1" << endl;
		return;
	}
	res = n - m - res;
	vector<int>ans;
	for (int i = 1; i <= n - m && res > 0; i++) {
		if (res > 0) {
			res--;
			a[i]++;
			ans.push_back(a[i] - 1);
			if (mp[a[i] - 1] > i) {
				if (mp[a[i] - 1] > n - m) {
					res++;
				}
				mp[a[i]] = max(mp[a[i]], mp[a[i] - 1]);
				swap(a[i], a[mp[a[i] - 1]]);
				mp[a[i]]--;
			}
		}
	}
	if (a[1 + n - m] > b[1]) {
		cout << "-1" << endl;
		return;
	}
	for (int i = m; i >= 1; i--) {
		if (a[i + n - m] < b[i]) {
			for (; a[i + n - m] < b[i] ;) {
				ans.push_back(a[i + n - m]);
				a[i + n - m]++;
			}
		}
	}
	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();
	}
}