#include <algorithm>
#include <cstdint>
#include <functional>
#include <ios>
#include <iostream>
#include <map>
#include <ostream>
#include <utility>

using namespace std;
using ll = int64_t;

template<class T,class P>
ostream&operator<<(ostream&os,map<T,P>const&m){
    os<<"map { ";
    for(auto [k,v]:m){
        os<<"{ "<<k<<", "<<v<<" }, ";
    }
    os<<"}";
    return os;
}
template<class T,class P>
ostream&operator<<(ostream&os,pair<T,P>const&m){
    os<<"pair { "<<m.first<<", "<<m.second<<" }";
    return os;
}


ll const maxn{ll(1e5+5)};
ll t,n,m,inf{ll(1)<<60};
ll q[maxn],qs{};
pair<ll, ll>e[maxn];

struct DSU{
    ll f[maxn];
    DSU(){for(ll i{1};i<=n;i++){f[i]=i;}}
    ll find(ll const&n){if(f[n]==n)return n; return f[n]=find(f[n]);}
    bool merge(ll const&a,ll const&b){if(find(a)==find(b))return false;f[find(a)]=find(b);return true;}
    friend ostream&operator<<(ostream&os,DSU const& d){
        os<<"DSU { ";
        for(ll i{1};i<=n;i++)os<<d.f[i]<<", ";
        os<<"}";
        return os;
    }
};
char dmem[sizeof(DSU)+1024];
DSU &dsu = *(DSU*)dmem;
ll un[maxn];

int main(){
    ios::sync_with_stdio(0),cin.tie(0),cout.tie(0);

    cin>>t;
    while(t--){
        cin>>n>>m;
        // cout<<n<<" "<<m<<'\n';
        for(ll i{1};i<=m;i++){
            ll u,v;
            cin>>u>>v;
            if(u>v)swap(u,v);
            // cout<<"uv "<<u<<' '<<v<<'\n';
            e[i].first=u,e[i].second=v;
        }
        sort(e+1,e+1+m,greater());
        new(dmem) DSU();
        // cout<<dsu<<'\n';
        ll uns{};
        for(ll i{1};i<=m;i++){
            // cout<<e[i]<<'\n';
            if(!dsu.merge(e[i].first, e[i].second)){
                un[++uns]=i;
            }
        }
        // cout<<dsu<<'\n';
        map<ll, ll> mm;
        for(ll i{1};i<=n;i++){
            mm[dsu.find(i)] = min(mm[dsu.find(i)]==0?inf:mm[dsu.find(i)],i);
        }
        // cout<<mm<<' '<<uns<<' '<<un[uns]<<' '<<e[un[uns]]<<'\n';
        // cout<<mm.size()<<' '<<uns<<'\n';
        if((ll)mm.size()-1>uns&&mm.size()!=1){
            cout<<"-1"<<'\n';
            continue;
        }
        if(mm.size()==1){
            cout<<"0\n";
            continue;
        }

        qs=0;
        for(auto const[k,v]:mm){
            q[++qs]=v;
        }
        sort(q+1,q+1+qs);
        // cout<<mm<<'\n';
        // for(ll i{1};i<=qs;i++)cout<<q[i]<<" ,";
        // cout<<'\n';
        // cout<<mm<<'\n';
        cout<<mm.size()-1<<'\n';
        for(ll i{2};i<=qs;i++){
            cout<<e[un[uns]].first<<" "<<e[un[uns]].second<<" "<<q[1]<<" "<<q[i]<<'\n';
            --uns;
        }
    }
}