#include<bits/stdc++.h>
#define ll long long
#define int long long
#define pii make_pair
#define pb push_back
#define rep(i,a,b) for(int i=a;i<=b;++i)
#define per(i,b,a) for(int i=b;i>=a;--i)
const ll inf = 1145141919810;
using namespace std;
inline ll read() {
    ll x=0,f=1;
    char c=getchar();
    while (c<'0' || c>'9') {
        if (c=='-')  f=-1;
        c=getchar();
    }
    while (c>='0' && c<='9') {
        x=x*10+c-'0';
        c=getchar();
    }
    return x*f;
}
inline void print(ll x) {
    if(x < 0) putchar('-'), x = -x;
    if(x > 9) print(x / 10);
    putchar(x % 10 + '0');
    return ;
}
inline void pprint(ll x) {
    print(x);
    puts("");
}
const int N = 4e5 + 7;
ll a[N], b[N];
bool cmp(ll x, ll y){
    return x > y;
}
void slv() {
    int n = read(), m = read();
    rep(i, 1, n) a[i] = read();
    rep(i, 1, m) b[i] = read();
    sort(a + 1, a + 1 + n, cmp);
    sort(b + 1, b + 1 + m, cmp);
    if(n < m){
        puts("-1");
        return ;
    }
    vector<int> q, qq;
    ll rst = n - m;
    rep(i, 1, m){
        if(a[i] > b[i]){
            puts("-1");
            return ;
        }
        if(b[i] - a[i] <= rst){
            rep(j, a[i], b[i] - 1){
                qq.pb(j);
            }
            rst -= b[i] - a[i];
        }else{
            puts("-1");
            return ;
        }
    }

    priority_queue<ll> _q;
    for(int i = n; i >= 1 && rst > 0; rst--, i--){
        if(a[i] > b[m]){
            puts("-1");
            return ;
        }
        q.pb(a[i]);
        _q.push(-a[i]);
    }
    for (auto i: qq) q.push_back(i);
    while(_q.size()){
        ll x = -_q.top();
        if(x >= b[m]) {
            puts("-1");
            return ;
        }
        _q.pop();
        x++;
        _q.push(-x);
        _q.pop();
    }
    pprint(q.size());

    for(auto x:q){
        print(x); putchar(' ');
    }
    puts("");
}
signed main() {
    int T = read();
    while(T--) {
        slv();
    }
    return 0;
}

/*
3
6 3
1 1 1 2 2 4
2 3 4

1
6 3
1 1 3 3 3 5
3 4 5
*/