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

#define ll long long
#define endl "\n"
const ll mod = 1e9 + 7;
const int N = 5e5 + 5;
const int inf = 0x3f3f3f3f;

void solve(){
	int n,m;
	cin>>n>>m;
	vector<int>a(n+1), 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());
	ll sum = 0;
	for(int i=n,j=m;j>=1;j--,i--){
		if(a[i] > b[j]){
			cout<<-1<<endl;
			return;
		}
		sum += b[j] - a[i];
	}
	ll s = 0;
	int dis = n - m;
	if(sum > dis){
		cout<<-1<<endl;
		return;
	}
	
	s = dis - sum;
	multiset<int>st;
	for(int i=1;i<=s;i++)st.insert(a[i]);
	vector<int>ans;
	int ma = 0;
	while(s-- && !st.empty()){
		int u = *st.begin();
		st.erase(st.begin());
		ans.push_back(u);
		u += 1;
		ma = max(ma, u);
		st.insert(u);
		ma = max(ma, *st.begin());
		st.erase(st.begin());
	}
	if(ma > b[1] || s > 0){
		cout<<-1<<endl;
		return;
	}
	
	for(int i=n,j=m;j>=1;j--,i--){
		int d = b[j] - a[i];
		while(d--){
			ans.push_back(a[i]++);
		}
	}
	cout<<ans.size()<<endl;
	for(auto &x:ans)cout<<x<<" ";cout<<endl;
}

signed main(){
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cout.tie(nullptr);
	
	int t = 1;
	cin>>t;
	for(int i=1;i<=t;i++)solve();
	return 0;
}