/*input
2
4 6
1 2 1
1 3 2
2 3 1
2 4 2
3 4 1
1 4 4
6 11
1 2 9
2 3 12
3 4 3
4 5 5
5 6 10
6 1 22
2 4 9
3 6 1
4 6 5
2 5 2
3 5 8
*/
#include<bits/stdc++.h>
using namespace std;
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
typedef tree<long long,null_type,less_equal<long long>,rb_tree_tag,tree_order_statistics_node_update> indexed_set;
//#pragma GCC target("avx2")
//order_of_key #of elements less than x
// find_by_order kth element
using ll=long long;
using ld=long double;
using pii=pair<ll,ll>;
#define f first
#define s second
#define pb push_back
#define REP(i,n) for(int i=0;i<n;i++)
#define REP1(i,n) for(ll i=1;i<=n;i++)
#define FILL(n,x) memset(n,x,sizeof(n))
#define ALL(_a) _a.begin(),_a.end()
#define sz(x) (int)x.size()
#define SORT_UNIQUE(c) (sort(c.begin(),c.end()),c.resize(distance(c.begin(),unique(c.begin(),c.end()))))
const ll maxn=1e5+5;
const ll maxlg=__lg(maxn)+2;
const ll INF64=4e18;
const int INF=0x3f3f3f3f;
const ll MOD=998244353;
const ld PI=acos(-1);
const ld eps=1e-6;
#define lowb(x) x&(-x)
#define MNTO(x,y) x=min(x,(__typeof__(x))y)
#define MXTO(x,y) x=max(x,(__typeof__(x))y)
template<typename T1,typename T2>
ostream& operator<<(ostream& out,pair<T1,T2> P){
    out<<P.f<<' '<<P.s;
    return out;
}
template<typename T>
ostream& operator<<(ostream& out,vector<T> V){
    REP(i,sz(V)) out<<V[i]+1<<((i!=sz(V)-1)?" ":"\n");
    return out;
}
ll mult(ll a,ll b){
    return a*b%MOD;
}
ll mypow(ll a,ll b){
    a%=MOD;
    if(a==0) return 0;
    if(b<=0) return 1;
    ll res=1LL;
    while(b){
        if(b&1) res=(res*a)%MOD;
        a=(a*a)%MOD;
        b>>=1;
    }
    return res;
}
vector<pii> g[maxn],v[maxn];
bool vis[maxn];
vector<int> top;
ll ds[maxn],dt[maxn];
int n;
void dfs(int u){
    if(vis[u]) return;
    vis[u]=1;
    for(auto x:v[u]){
        if(dt[x.f]+ds[u]+x.s==ds[n-1]){
            g[u].pb(x);
            dfs(x.f);
        }
    }
    top.pb(u);
}
int mx;
void dfs2(int u){
    if(vis[u]) return;
    vis[u]=1;
    for(auto x:v[u]){
        if(dt[x.f]+ds[u]+(x.s==mx)==ds[n-1]){
            if(x.s==mx) x.s=0;
            g[u].pb(x);
            dfs2(x.f);
        }
    }
}
void dij(int u,ll dist[]){
    priority_queue<pii,vector<pii>,greater<pii>> pq;
    REP(i,n) dist[i]=INF64;
    dist[u]=0;
    pq.push({0,u});
    while(sz(pq)){
        int z=pq.top().s;
        if(pq.top().f>dist[z]){
            pq.pop();
            continue;
        }
        pq.pop();
        for(auto x:v[z]){
            if(dist[x.f]>dist[z]+x.s){
                dist[x.f]=dist[z]+x.s;
                pq.push({dist[x.f],x.f});
            }
        }
    }
}
void solve(){
    int m;
    cin>>n>>m;
    REP(i,n) v[i].clear(),g[i].clear(),vis[i]=0;
    top.clear();
    REP(i,m){
        int a,b,c;
        cin>>a>>b>>c;
        --a,--b;
        v[a].pb({b,c}),v[b].pb({a,c});
    }
    dij(0,ds);
    dij(n-1,dt);
    dfs(0);
    REP(i,n) v[i]=g[i],g[i].clear();
    //REP(i,n) cout<<i<<':'<<v[i]<<'\n';
    REP(a,300){
        mx=0;
        REP(i,n){
            vis[i]=0;
            for(auto x:v[i]){
                MXTO(mx,x.s);
            }
        }
        if(mx==0) break;
        REP(i,n) ds[i]=dt[i]=-INF;
        ds[0]=dt[n-1]=0;
        for(int x:top){
            for(auto a:v[x]){
                MXTO(dt[x],dt[a.f]+(a.s==mx));
            }
        }
        reverse(ALL(top));
        for(int x:top){
            for(auto a:v[x]){
                MXTO(ds[a.f],ds[x]+(a.s==mx));
            }
        }
        reverse(ALL(top));
        dfs2(0);
        REP(i,n) v[i]=g[i],g[i].clear();
    }
    int p=0;
    vector<int> ans;
    while(p!=n-1){
        assert(sz(v[p]));
        ans.pb(p);
        p=v[p][0].f;
    }
    ans.pb(n-1);
    cout<<sz(ans)<<'\n';
    cout<<ans;
}
int main(){
    ios::sync_with_stdio(false),cin.tie(0);
    int t;
    cin>>t;
    while(t--) solve();
}