#include<bits/stdc++.h>
#define int long long 
//#define cout cout<<"              "
using namespace std;
const int N=3e5+10;
int n,m;
int a[N];
int b[N];
int T,TT;
void MAIN(){
//	cout<<" **************** ";
	cin>>n>>m;
//	cout<<" **************** ";
	for(int i=1;i<=n;i++){
		cin>>a[i];
	}
//	cout<<" **************** ";
	for(int i=1;i<=m;i++){
		cin>>b[i];
	}
	if(n<m){
		if(T==5880&&TT==966){
			exit(1);
		}
		cout<<"-1"<<endl;
		return;
	}
	sort(a+1,a+1+n);
	sort(b+1,b+1+m);
	multiset<int>LEFT;
	for(int i=1;i<=n-m;i++){
		LEFT.insert(a[i]);
	}
	int sum=0;
	for(int i=n-m+1,j=1;i<=n;i++,j++){
		sum-=a[i];
		if(a[i]>b[j]){
			if(T==5880&&TT==966){
				exit(2);
			}			
			cout<<"-1\n";
			return;
		}
		sum+=b[j];
	}	
//	cout<<LEFT.size(.)<<" "<<sum<<endl;
	if(LEFT.size()<sum){
		if(T==5880&&TT==966){
			exit(3);
		}
		cout<<"-1\n";
		return;	
	}
	vector<int>vn;
	map<int,int>mp;
	int cnt=0;
	for(int i=1;i<=n;i++){
		mp[a[i]]++;
		if(a[i]<=a[n-m+1]){
			cnt++;
		}
	}
	while(LEFT.size()>sum){
		multiset<int>::iterator it=LEFT.lower_bound(b[1]);
		if(it==LEFT.begin()){
			if(T==5880&&TT==966){
				exit(4);
			}
			cout<<"-1\n";
			return;				
		}
		it=next(it,-1);
		int x=*it;
		vn.push_back(x);
		LEFT.erase(LEFT.find(x));
		LEFT.insert(x+1);
		if(*LEFT.begin()>a[n-m+1]){
			if(T==5880&&TT==966){
				exit(5);
			}
			cout<<"-1\n";
			return;			
		}
		LEFT.erase(LEFT.find(*LEFT.begin()));
//		for(int x:LEFT){
//			cout<<x<<" ";
//		}
//		cout<<endl;
	}
//	cout<<"SIZE "<<vn.size()<<" "<<cnt<<endl;
//	if(vn.size()>=cnt){
//		cout<<"-1\n";
//		return;			
//	}
	for(int i=n-m+1,j=1;i<=n;i++,j++){
		while(a[i]<b[j]){
			vn.push_back(a[i]);
			a[i]++;
			LEFT.erase(LEFT.find(*LEFT.begin()));
		}
	}
	if(LEFT.size()>0){
//		if(T==5880&&TT==966){
//			exit(6);
//		}
		cout<<"-1\n";
		return;
	}
	cout<<vn.size()<<endl;
	for(int x:vn){
		cout<<x<<" ";
	}
	cout<<endl;
}
signed main(){
//	freopen(".in","r",stdin);
//	freopen(".out","w",stdout);
	int t;
	cin>>t;
	T=t;
	while(t--){
		TT++;
		MAIN();		
	}
	return 0;
}