#include <bits/stdc++.h>
#define int long long
#define debug puts("###");
using namespace std;

const int N=3e5+10;
int a[N],b[N],A[N],B[N],n,m; 


inline void solve() {
	memset(a,0,sizeof(a));
	memset(b,0,sizeof(b));
	for (int i=1;i<=n;i++) a[i]=A[i];
	for (int i=n-m+1,j=1;i<=n;i++,j++) b[i]=B[j];
	sort(a+1,a+n+1);
	sort(b+n-m+1,b+n+1);
	for (int i=n-m+1;i<=n;i++) if (a[i]>b[i]) {puts("-1");return ;}
	int suma=0,sumb=0;
	for (int i=n-m+1;i<=n;i++) suma+=a[i],sumb+=b[i];
	int step=sumb-suma,minb=b[n-m+1];
	if (step>n-m) {puts("-1");return ;} 
	priority_queue<int,vector<int>,greater<int> > q,q2;
	for (int i=1;i<=n-m;i++) q.push(a[i]);
	vector<int> v;
	for (int i=n-m+1;i<=n;i++) if (a[i]!=b[i]) v.push_back(i);
	int len=v.size();
	for (int i=n-m+1,j=0;j<len;i++,j++) b[i]=b[v[j]],q2.push(a[v[j]]);
	vector<int> ans;
	for (int i=n-m,cnt=n-m+1;i>=1;i--) {
		int x=q.top(),y=-1; q.pop();
		if (!q2.empty()) y=q2.top();
		if (x>=minb) {puts("-1");return ;}
		if (x==y) {
			q2.pop(); --step; ans.push_back(y);
			if (y+1==b[cnt]) ++cnt;
			else q2.push(y+1);
		}
		else {
			q.push(x+1); ans.push_back(x); q.pop();
		}
		if (i-1==step) {
			while (!q2.empty()) {
				int y=q2.top(); q2.pop();
				ans.push_back(y); if(y+1==b[cnt]) ++cnt;
				else q2.push(y+1);
			}
			break;
		}
	}
	
	len=ans.size();
	printf("%lld\n",len);
	for (int i=0;i<len;i++) printf("%lld ",ans[i]);if (len!=0) puts("");
}

void solve2(){
	vector<int>ans;
	for(int i=1;i<=n;++i) a[i]=A[i];
	for(int i=1;i<=m;++i) b[i]=B[i];
	sort(a+1,a+n+1),sort(b+1,b+m+1);
	int suma=0,sumb=0,minn=b[1],cur=1;
	for(int i=1;i<=m;++i)if(a[i+n-m]>b[i]){solve();return;}
	for(int i=1;i<=m;++i)sumb+=b[i],suma+=a[n-i+1];
	for(int i=1;i<=m;++i){
		if(i==1||b[i]==b[i-1])while(a[n-m+i]<b[i])ans.push_back(a[n-m+i]),++a[n-m+i],++cur,++suma;
		else break;
	}
	for(int i=1;i<=m;++i)if(a[n-m+i]<b[1])ans.push_back(a[n-m+i]),++a[n-m+i],++cur,++suma;
	/*
	int sum=0,flag=0;
	for(int i=1;i<=n-m;++i)sum+=(a[n-m+1]-a[i]);
	if(sumb-suma>sum&&b[1]!=a[n-m+1]){ans.push_back(a[n-m+1]);a[n-m+1]++;++suma;minn++;flag=1;}
	else if(sumb-suma>sum&&b[1]==a[n-m+1]){cout<<"-1\n";return;}
  */
	if(suma>sumb){solve();return;}
	if(sumb-suma>n-m-cur+1){solve();return;}
	priority_queue<int,vector<int>,greater<int> >q;
	for(int i=cur;i<=n-m;++i)q.push(a[i]);
	for(int i=1;i<=(n-m)-(sumb-suma)-cur+1;++i){
		if(q.empty()){solve();return;}
		int t=q.top();q.pop();
		if(t>=minn){solve();return;}
		ans.push_back(t);
		q.push(t+1);q.pop();
	}
	for(int i=1;i<=m;++i)while(a[i+n-m]<b[i])ans.push_back(a[i+n-m]),++a[i+n-m];
	cout<<ans.size()<<endl;
	for(int i:ans)cout<<i<<' ';cout<<endl;
}

signed main(void) {
	int t; cin>>t;
	while (t--) {
		cin>>n>>m;
		for (int i=1;i<=n;i++) cin>>A[i];
		for (int i=1;i<=m;i++) cin>>B[i];
		solve2();
	}
}