#include <algorithm>
#include <iostream>
#include <cstring>
#include <cstdio>
#include <cmath>
#define FOR() ll le=e[u].size();for(ll i=0;i<le;i++)
#define QWQ cout<<"QwQ\n";
#define ll long long
#include <vector>
#include <queue>
#include <unordered_map>

using namespace std;
const ll N=501010;
const ll qwq=303030;
const ll inf=0x3f3f3f3f;

inline ll read() {
    ll sum = 0, ff = 1; char c = getchar();
    while(c<'0' || c>'9') { if(c=='-') ff = -1; c = getchar(); }
    while(c>='0'&&c<='9') { sum = sum * 10 + c - '0'; c = getchar(); }
    return sum * ff;
}

ll T;
ll n,m,K;
vector <ll> e[N];
unordered_map <ll,ll> f;
ll tot;
ll fa[N],zhi[N];
ll st[N],cnt;

ll find(ll x) { return fa[x]==x ? x : fa[x]=find(fa[x]); }

ll _id(ll h,ll x) {
    return (h-1) * n + x;
}

inline bool check(ll h,ll x,ll y) {
    ll u = _id(h,x), v = _id(h,y);
    if(f.find(u)==f.end() || f.find(v)==f.end()) return 0;
    ll xx = find(f[u]), yy = find(f[v]);
    if(xx==yy) return 1;
    return 0;
}

bool link = 0;
void DFS(ll u,ll ff,ll goal) {
    st[++cnt] = u;
    if(goal==u) { link = 1; return ; }
    for(ll v : e[u]) {
        if(v==ff) continue;
        DFS(v,u,goal);
        if(link) return ;
    }
    if(!link) cnt--;
}

void chushihua() {
    f.clear();
    for(ll i=1;i<=tot;i++) e[i].clear();
    tot = 0;
}

int main() {
    ll x,y;
    T = read();
    while(T--) {
        chushihua();
        n = read(); m = read();
        for(int i=1;i<=2*m;i++) fa[i] = i;
        K = m/(n-1);
        if(m%(n-1)) K++;
        ll ans1 = 0, ans2 = 0;
        while(m--) {
            x = read(); y = read();
            if(ans1) continue;
            ll l = 1, r = K-1, mid, res = 0;
            while(l<=r) {
                mid = l+r >> 1;
                if(check(mid,x,y)) l = mid+1, res = mid;
                else r = mid-1;
            }
            ll u = _id(res+1,x), v = _id(res+1,y);
            if(f.find(u)==f.end()) f[u] = ++tot, zhi[tot] = x;
            if(f.find(v)==f.end()) f[v] = ++tot, zhi[tot] = y;
            fa[ f[u] ] = f[v];
            e[ f[u] ].push_back( f[v] );
            e[ f[v] ].push_back( f[u] );
            if(res+1==K) ans1 = x, ans2 = y;
        }
        cout<<ans2<<" "<<ans1<<"\n";
        for(ll i=1;i<=K;i++) {
            ll u = f[_id(i,ans1)], v = f[_id(i,ans2)];
            link = 0;
            DFS(u,u,v);
            cout<<cnt<<" ";
            while(cnt) cout<<zhi[st[cnt--]]<<" ";
            cout<<"\n";
        }
    }
    return 0;
}