#include<bits/stdc++.h>
using namespace std;
const int N=3e5+5;
int T;
int n,m;
int a[N];
int b[N];
bool cmp(int a,int b)
{
	return a>b;
}
void solve()
{
	cin>>n>>m;
	for(int i=1;i<=n;i++)
	{
		cin>>a[i];
	}
	for(int i=1;i<=m;i++)
	{
		cin>>b[i];
	}
	vector<int>ans;
	sort(a+1,a+n+1,cmp);
	sort(b+1,b+m+1,cmp);
	int add=0,del=0;
	multiset<int>u,v;
	for(int i=1;i<=m;i++)
	{
		if(a[i]>b[i])
		{
			cout<<"-1"<<endl;
			return;
		}
		add+=b[i]-a[i];
		u.insert(a[i]);
	}
	for(int i=m+1;i<=n;i++)
	{
		del++;
		v.insert(a[i]);
	}
	if(add-del>0)
	{
		cout<<"-1"<<endl;
		return;
	}
	while(del>0&&del-add>0)
	{
//		cout<<del<<"----"<<add<<endl;
//		for(auto op:u)cout<<op<<" ";cout<<endl;
//		for(auto op:v)cout<<op<<" ";cout<<endl;
		auto x=v.begin();
		auto y=u.begin();
		v.erase(x);
		ans.push_back(*x);
		if(*x+1>*y)
		{
			u.erase(y);
			v.insert(*y);
			u.insert(*x+1);
			add--;
		}
		else
		{
			v.insert(*x+1);
		}
		v.erase(v.begin());
		del--;
	}
	int ok=1;
	for(int i=m;i>=1;i--)
	{
		auto x=u.begin();
		a[i]=*x;
		u.erase(x);
	}
	for(int i=1;i<=m;i++)
	{
		if(a[i]>b[i])
		{
			cout<<"-1"<<endl;
			return;
		}
		while(a[i]<b[i])
		{
			ans.push_back(a[i]);
			a[i]++;
		}
	}
	cout<<ans.size()<<endl;
	for(auto x:ans)
	{
		cout<<x<<" ";
	}
	cout<<endl;
}
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	cout.tie(0);
	cin>>T;
	while(T--)
	{
		solve();
	}
}