#include <bits/stdc++.h>
using namespace std;
#define endl '\n'
#define yes cout << "YES\n"
#define no cout << "NO\n";
#define ll long long
#define ull unsigned long long
#define pii pair<int, int>
const int MAX = 3e5 + 10, inf = 2147483647, mod = 998244353;

void solve(){
	int n, m;
	cin >> n >> m;
	vector<int> a(n), b(m);
	for (int i = 0; i < n; ++ i) cin >> a[i];
	for (int i = 0; i < m; ++ i) cin >> b[i];
	sort(a.begin(), a.end(), greater<int>());
	sort(b.begin(), b.end(), greater<int>());
	multiset<int> s1;
	multiset<pii> s2;
	vector<int> ans;
	ll d = 0;
	bool flag = 0;
	for (int i = 0; i < m; ++ i){
		if (a[i] > b[i]) flag = 1;
		d += b[i] - a[i];
	}
	if (flag or d > n - m){
		cout << -1 << endl;
		return;
	}
	for (int i = 0; i < m; ++ i){
		if (a[i] != b[i]) s2.insert({a[i], b[i]});
	}
	for (int i = m; i < n; ++ i) s1.insert(a[i]);
	for (int i = 0; i < n - m - d; ++ i){
		while (not s2.empty() and *s1.begin() + 1 > s2.begin()->first){ //保证材料的安全
			auto [x, y] = *s2.begin();
			s2.erase({x, y});
			ans.push_back(x);
			x ++;
			if (x != y) s2.insert({x, y});
			s1.erase(s1.begin());
		}
		if (s1.empty() or *s1.begin() + 1 > b.back()){//无法再删或者要把材料删掉
			cout << -1 << endl;
			return;
		}
		//消耗冗余
		int t = *s1.begin();
		ans.push_back(t);
		s1.erase(s1.begin());
		s1.insert(t + 1);
		s1.erase(s1.begin());
	}
	for (auto [x, y]: s2){
		for (int i = x; i < y; ++ i) ans.push_back(i);
	}
	cout << ans.size() << endl;
	for (int x: ans) cout << x << ' ';
	cout << endl;
}
int main(){
    ios::sync_with_stdio(0);cin.tie(0);cout.tie(0);
	//cout << fixed << setprecision(6);
	int _;cin>>_;while (_ --)
		solve();
}