// #pragma GCC optimize("Ofast,no-stack-protector,unroll-loops",
// "omit-frame-pointer", "inline") #pragma GCC
// target("sse,sse2,sse3,ssse3,sse4,sse4.1,sse4.2,popcnt,abm,mmx,avx,avx2,fma,tune=native")
// #pragma GCC option("arch=native", "no-zero-upper") // Enable AVX

/// UH Top
#include <bits/stdc++.h>
#define db(x)   cerr << #x << ':' << (x) << '\n';
#define all(v)  (v).begin(), (v).end()
#define allr(v) (v).rbegin(), (v).rend()
// #define int ll
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
// typedef __int128_t int128;
typedef pair<ll, ll> pii;
typedef pair<ld, ll> pdi;
typedef pair<ld, ld> pdd;
typedef pair<ld, pdd> pdp;
typedef pair<string, ll> psi;
typedef pair<ll, string> pls;
typedef pair<string, string> pss;
typedef pair<ll, pii> pip;
typedef pair<pii, pii> ppp;
typedef complex<ld> point;
typedef vector<point> polygon;
typedef vector<ll> vi;
typedef pair<point, int> ppi;
#define prec(n)                                                                \
	cout.precision(n);                                                         \
	cout << fixed
const ll mod = (1e9 + 7);
const ld eps = (1e-9);
const ll oo = (ll)(1e18 + 5);
#define pi   acos(-1)
#define MAXN (ll)(1e6 + 5)
#define pb push_back
#define fs first
#define sc second
int n, m;

void problem(){
		cin >> n >> m;
		vector<int> a(n);
		map<int,int> M;
		for (int i = 0; i < n; i++){
			cin >> a[i];
			M[a[i]]++;
		}
		vector<int> b(m);
		for (int i = 0; i < m; i++)
			cin >> b[i];

		sort(allr(a));
		sort(allr(b));
		int sum=0;

		for(int i=0;i<m;i++){
			if(b[i]<a[i]){
				cout<<-1<<'\n';
				return;
			}
			sum+=b[i]-a[i];
		}
		int d=a[m-1];
		if(sum>n-m){
			cout<<"-1\n";
			return;
		}
		int extra=n-m-sum;
		vi Ops;
		int tot=n;
		while(tot-m-sum){
			int val=M.begin()->fs;
			Ops.pb(val);
			M[val+1]++;
			M[val]--;
			int rem=M[val];
			if(rem==tot-m){
				sum--;
			}
			if(sum<0){
				cout<<-1<<'\n';
				return;
			}
			if((M.begin()->sc)==0){
			  M.erase(M.begin());	
			}
			val=M.begin()->fs;
			M[val]--;
			if((M.begin()->sc)==0){
			  M.erase(M.begin());	
			}
			tot--;
			if(M.size()==0){
				cout<<-1<<'\n';
				return;
			}
		}
		
		a.resize(0);
		for(auto p:M){
			for(int j=0;j<p.sc;j++){
				a.pb(p.fs);
			}
		}	
		reverse(all(a));
		for(int i=0;i<m;i++){
			if(a[i]>b[i]){
				cout<<-1<<'\n';
				return;
			}
			for(int j=a[i];j<b[i];j++)Ops.pb(j);
		}
		cout<<Ops.size()<<'\n';
		for(auto a:Ops){
			cout<<a<<' ';
		}
		cout<<'\n';
}

int32_t main() {
	ios_base::sync_with_stdio(0);
	cin.tie(0);

	int t;
	cin >> t;
	while (t--) {
		problem();
	}

	return 0;
}