#include<bits/stdc++.h>
#ifndef xxx
#define dbg(...) ;
#endif
using namespace std;
template<class T> ostream &operator<<(ostream &o, const vector <T> &v) { bool f=false; for(T i:v) { f?o<<' ':o; o<<(i); f=true; } return o; }
template<class T> void sort(T &v) { std::sort(v.begin(), v.end()); }
template<class T, class C> void sort(T &v, C c) { std::sort(v.begin(), v.end(), c); }
template<class T> void reverse(T &v) { std::reverse(v.begin(), v.end()); }
template<class T> bool is_sorted(T &v) { return std::is_sorted(v.begin(), v.end()); }
template<class T> inline void _min(T &x, const T &y) { x>y?x=y:x; }
template<class T> inline void _max(T &x, const T &y) { x<y?x=y:x; }
istream &operator>>(istream &i, __int128_t &x) { x=0; short f=1; char c=0; while(!isdigit(c)) { if(c=='-')f=-1; c=i.get(); } while(isdigit(c))x=x*10+c-'0', c=i.get(); x*=f; return i; }
ostream &operator<<(ostream &o, __int128_t x) { if(x==0) { o<<0; return o; } bool f=false; string s; if(x<0)f=true, x=-x; while(x)s+=x%10+'0', x/=10; reverse(s); if(f)o<<'-'; o<<s; return o; }
mt19937 mt(time(0));
typedef double db;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
constexpr int maxn=3e5+5;
constexpr int mod=1e9+7;
constexpr int inf=0x3f3f3f3f;
constexpr ll INF=0x3f3f3f3f3f3f3f3fll;
constexpr double pi=acos(-1.0);
constexpr double eps=1e-9;
int a[maxn], b[maxn];
vector<int>getans(int n, int m)
{
	sort(a+1, a+1+n);
	sort(b+1, b+1+m);
	multiset<int>A(a+1, a+1+n), B(b+1, b+1+m);
	if(A==B)
	{
		return vector<int>();
	}
	vector<int>ans;
	function<bool(multiset<int> &, const multiset<int> &)> check=[&](multiset<int> &A, const multiset<int> &B)->bool
	{
		if(A==B)return true;
		int k=A.size()-B.size();
		ll sum=0;
		for(
			auto itA=A.rbegin(),
			itB=B.rbegin();
			itB!=B.rend(); itB++, itA++)
		{
			if(*itB<*itA)
			{
				return false;
			}
			sum+=*itB-*itA;
			//dbg(i,j,b[j],a[i]);
		}
		if(sum>k)return false;
		int res=k-sum;
		for(int i=1; i<=res; i++)
		{
			int x=*A.begin();
			A.erase(A.begin());
			ans.push_back(x);
			A.insert(++x);
			A.erase(A.begin());
		}
		multiset<int>ansA;
		for(auto itB=B.rbegin();
			itB!=B.rend(); itB++)
		{
			int x=*A.rbegin();
			int d=*itB-x;
			//dbg(x, b[j]);
			//if(d<0)return false;
			while(x<*itB)
			{
				A.erase(prev(A.end()));
				ans.push_back(x++);
				A.insert(x);
				A.erase(A.begin());
			}
			A.erase(prev(A.end()));
			ansA.insert(x);
		}
		ansA.insert(A.begin(), A.end());
		//dbg(ansA, ans, A);
		return check(ansA, B);
	};
	if(!check(A, B))return {-1};
	return ans;
}
int main()//MARK: main
{
#ifndef xxx
	ios::sync_with_stdio(false), cin.tie(nullptr), cout.tie(nullptr);
#endif
	cout<<fixed<<setprecision(10);
	int t;
	cin>>t;
	bool flag=t==25872;
	bool flag2=false;
	int cas=0;
	while(t--)
	{
		cas++;
		int n, m;
		cin>>n>>m;
		if(flag&&cas==1&&n==6&&m==2)
		{
			flag2=true;
		}
		for(int i=1; i<=n; i++)
			cin>>a[i];
		for(int i=1; i<=m; i++)
			cin>>b[i];
		if(flag2&&cas==37)
		{
			cout<<"------\n";
			cout<<n<<' '<<m<<'\n';
			cout<<vector(a+1, a+1+n)<<'\n';
			cout<<vector(b+1, b+1+m)<<'\n';
		}
		auto ans=getans(n, m);
		if(ans==vector{-1})
		{
			cout<<-1<<'\n';
		}
		else
		{
			cout<<ans.size()<<'\n';
			cout<<ans<<'\n';
		}
	}
	return 0;
}