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

#define dbg(x...) \
do { \
std::cout << #x << " -> "; \
err(x); \
} while (0)

void err() {
	std::cout << std::endl;
}

template<class T, class... Ts>
void err(T arg, Ts &... args) {
	std::cout << fixed << setprecision(10) << arg << ' ';
	err(args...);
}

void GENSHEN_START() {
	int n,m;cin >> n >> m;
	vector <int> a(n + 5),b(m + 5);
	int cnt1 = 0;
	for (int i = 1;i <= n;i++) cin >> a[i];
	for (int i = 1;i <= m;i++) cin >> b[i];
	sort(a.begin() + 1,a.begin() + 1 + n);
	sort(b.begin() + 1,b.begin() + 1 + m);
	for (int i = 1;i <= m;i++) cnt1 += (b[i] == b[1]);
	int lst = -1,ok = 0;
	for (int i = 1;i <= n;i++) {
		if (a[i] < b[1]) lst = i;
	}
	vector<int>ans;
	int l = 1;
	int val = -1,mod = 0,cnt = 0;
	for (int i = lst;i >= 1;i--) {
		int x = a[i];
		if (b[1] - x <= i - l) {
			cnt++;
			while (x != b[1]) {
				ans.push_back(x);
				x++;
				l++;
			}
		}
		else {
			val = x;
			mod = i - l + 1;
			break;
		}
	}
	vector<int>c;
	int cnt2 = 0;
	while (cnt) {
		c.push_back(b[1]);
		cnt--;
		cnt2++;
	}
	for (int i = 1;i <= n;i++) {
		if (a[i] >= b[1]) c.push_back(a[i]);
		cnt2 += (a[i] == b[1]);
	}
	//for (auto i : c) dbg(i);
	//dbg(mod);
	int len = c.size();
	if (cnt2 < cnt1) {
		cout << "-1" << '\n';
		return ;
	}
	if (len - (cnt2 - cnt1) > m) {
		cout << "-1" << '\n';
		return ;
	}
	int all = len - m,sum = 0;
	for (int i = len - m;i < len;i++) {
		if (c[i] > b[i - len + m + 1]) {
			cout << "-1" << '\n';
			return ;
		}
		sum += b[i - len + m + 1] - c[i];
	}
	if (sum >= all && sum <= all + mod) {
		for (int i = 1;i <= mod - (sum - all);i++) {
			ans.push_back(val);
			val++;
		}
		for (int i = len - m;i < len;i++) {
			while (c[i] < b[i - len + m + 1]) {
				ans.push_back(c[i]);
				c[i]++;
			}
		}
		cout << ans.size() << '\n';
		for (auto i : ans) cout << i << ' ';
		cout << '\n';
	}
	else {
		cout << "-1" << '\n';
	}
}

signed main()
{
	ios::sync_with_stdio(false);cin.tie(nullptr);
	int T = 1;
	cin >> T;
	while (T--) GENSHEN_START();
	return 0;
}