#include<bits/stdc++.h>
#define L(i, j, k) for(int i = (j); i <= (k); ++i)
#define R(i, j, k) for(int i = (j); i >= (k); --i)
#define ll long long
#define vi vector <int>
#define sz(a) ((int) (a).size())
#define me(f, x) memset(f, x, sizeof(f))
#define uint unsigned int
#define ull unsigned long long 
#define i128 __int128
using namespace std;
const int N = 1e6 + 7, mod = 998244353; 
int m, n;
int a[N], b[N];
void Main() {
	cin >> n >> m;
	L(i, 1, n) cin >> a[i];
	L(i, 1, m) cin >> b[i];
	sort(a + 1, a + n + 1);
	reverse(a + 1, a + n + 1);
	sort(b + 1, b + m + 1);
	reverse(b + 1, b + m + 1);
	L(i, 1, m) {
		if(a[i] > b[i]) {
			cout << "-1\n";
			return ; 
		}
	}
	ll sum = 0;
	L(i, 1, m) {
		sum += b[i] - a[i];
	}
	int pos = 1;
	vi L;
	int nes = n;
	R(t, n, m + 1) {
		if(sum >= t - m) {
			while(pos <= n && a[pos] == b[pos]) ++pos;
			if(pos > t) {
				cout << -1 << '\n';
				return ;
			}
			L.emplace_back(a[pos]);
			++a[pos];
			--sum;
		} else {
			while(nes > 1 && a[nes - 1] == a[nes]) --nes;
			L.emplace_back(a[nes]);
			++a[nes];
			++nes, nes = min(nes, t - 1);
		}
//		L(i, 1, t)
//			cout << a[i] << ",";
//		cout<<'\n';
	} 
	L(i, 1, m) 
		if(a[i] != b[i]) {
			cout << -1 << '\n';
			return ;
		}
	cout << sz(L) << '\n';
	for(auto&u : L)
		cout << u << ' ';
	cout << '\n';
}
int main () {
	ios :: sync_with_stdio(false);
	cin.tie(0); cout.tie(0);
	int t; cin >> t; while(t--) Main();
	return 0;
}