#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include<iostream>
#include<string>
#include<cstdio>
#include<vector>
#include<cmath>
#include<algorithm>
#include<functional>
#include<iomanip>
#include<queue>
#include<ciso646>
#include<random>
#include<map>
#include<set>
#include<bitset>
#include<stack>
#include<unordered_map>
#include<unordered_set>
#include<utility>
#include<cassert>
#include<complex>
#include<numeric>
#include<array>
#include<chrono>
using namespace std;

//#define int long long
typedef long long ll;

typedef unsigned long long ul;
typedef unsigned int ui;
constexpr ll mod = 998244353;
//constexpr ll mod = 1000000007;
const ll INF = mod * mod;
typedef pair<int, int>P;

#define rep(i,n) for(int i=0;i<n;i++)
#define per(i,n) for(int i=n-1;i>=0;i--)
#define Rep(i,sta,n) for(int i=sta;i<n;i++)
#define rep1(i,n) for(int i=1;i<=n;i++)
#define per1(i,n) for(int i=n;i>=1;i--)
#define Rep1(i,sta,n) for(int i=sta;i<=n;i++)
#define all(v) (v).begin(),(v).end()
typedef pair<ll, ll> LP;

template<typename T>
void chmin(T& a, T b) {
	a = min(a, b);
}
template<typename T>
void chmax(T& a, T b) {
	a = max(a, b);
}
template<typename T>
void cinarray(vector<T>& v) {
	rep(i, v.size())cin >> v[i];
}
template<typename T>
void coutarray(vector<T>& v) {
	rep(i, v.size()) {
		if (i > 0)cout << " "; cout << v[i];
	}
	cout << "\n";
}
ll mod_pow(ll x, ll n, ll m = mod) {
	if (n < 0) {
		ll res = mod_pow(x, -n, m);
		return mod_pow(res, m - 2, m);
	}
	if (abs(x) >= m)x %= m;
	if (x < 0)x += m;
	//if (x == 0)return 0;
	ll res = 1;
	while (n) {
		if (n & 1)res = res * x % m;
		x = x * x % m; n >>= 1;
	}
	return res;
}
//mod should be <2^31
struct modint {
	int n;
	modint() :n(0) { ; }
	modint(ll m) {
		if (m < 0 || mod <= m) {
			m %= mod; if (m < 0)m += mod;
		}
		n = m;
	}
	operator int() { return n; }
};
bool operator==(modint a, modint b) { return a.n == b.n; }
bool operator<(modint a, modint b) { return a.n < b.n; }
modint operator+=(modint& a, modint b) { a.n += b.n; if (a.n >= mod)a.n -= (int)mod; return a; }
modint operator-=(modint& a, modint b) { a.n -= b.n; if (a.n < 0)a.n += (int)mod; return a; }
modint operator*=(modint& a, modint b) { a.n = ((ll)a.n * b.n) % mod; return a; }
modint operator+(modint a, modint b) { return a += b; }
modint operator-(modint a, modint b) { return a -= b; }
modint operator*(modint a, modint b) { return a *= b; }
modint operator^(modint a, ll n) {
	if (n == 0)return modint(1);
	modint res = (a * a) ^ (n / 2);
	if (n % 2)res = res * a;
	return res;
}

ll inv(ll a, ll p) {
	return (a == 1 ? 1 : (1 - p * inv(p % a, a)) / a + p);
}
modint operator/(modint a, modint b) { return a * modint(inv(b, mod)); }
modint operator/=(modint& a, modint b) { a = a / b; return a; }
const int max_n = 1 << 2;
modint fact[max_n], factinv[max_n];
void init_f() {
	fact[0] = modint(1);
	for (int i = 0; i < max_n - 1; i++) {
		fact[i + 1] = fact[i] * modint(i + 1);
	}
	factinv[max_n - 1] = modint(1) / fact[max_n - 1];
	for (int i = max_n - 2; i >= 0; i--) {
		factinv[i] = factinv[i + 1] * modint(i + 1);
	}
}
modint comb(int a, int b) {
	if (a < 0 || b < 0 || a < b)return 0;
	return fact[a] * factinv[b] * factinv[a - b];
}
modint combP(int a, int b) {
	if (a < 0 || b < 0 || a < b)return 0;
	return fact[a] * factinv[a - b];
}

ll gcd(ll a, ll b) {
	a = abs(a); b = abs(b);
	if (a < b)swap(a, b);
	while (b) {
		ll r = a % b; a = b; b = r;
	}
	return a;
}
using ld = long double;
//typedef long double ld;
typedef pair<ld, ld> LDP;
const ld eps = 1e-10;
const ld pi = acosl(-1.0);
template<typename T>
void addv(vector<T>& v, int loc, T val) {
	if (loc >= v.size())v.resize(loc + 1, 0);
	v[loc] += val;
}
/*const int mn = 2000005;
bool isp[mn];
vector<int> ps;
void init() {
	fill(isp + 2, isp + mn, true);
	for (int i = 2; i < mn; i++) {
		if (!isp[i])continue;
		ps.push_back(i);
		for (int j = 2 * i; j < mn; j += i) {
			isp[j] = false;
		}
	}
}*/

//[,val)
template<typename T>
auto prev_itr(set<T>& st, T val) {
	auto res = st.lower_bound(val);
	if (res == st.begin())return st.end();
	res--; return res;
}

//[val,)
template<typename T>
auto next_itr(set<T>& st, T val) {
	auto res = st.lower_bound(val);
	return res;
}
using mP = pair<modint, modint>;
mP operator+(mP a, mP b) {
	return { a.first + b.first,a.second + b.second };
}
mP operator+=(mP& a, mP b) {
	a = a + b; return a;
}
mP operator-(mP a, mP b) {
	return { a.first - b.first,a.second - b.second };
}
mP operator-=(mP& a, mP b) {
	a = a - b; return a;
}
LP operator+(LP a, LP b) {
	return { a.first + b.first,a.second + b.second };
}
LP operator+=(LP& a, LP b) {
	a = a + b; return a;
}
LP operator-(LP a, LP b) {
	return { a.first - b.first,a.second - b.second };
}
LP operator-=(LP& a, LP b) {
	a = a - b; return a;
}

mt19937 mt(time(0));

const string drul = "DRUL";
string senw = "SENW";
//DRUL,or SENW
int dx[4] = { 1,0,-1,0 };
int dy[4] = { 0,1,0,-1 };
//-----------------------------------------


bool isp(int x) {
	if (x == 1)return false;
	for (int i = 2; i * i <= x; i++) {
		if (x % i == 0)return false;
	}
	return true;
}
//1.1*10^9だと2.2*10^9がintでoverflowする
mt19937 mtle(time(0));
uniform_int_distribution<> udle(900000000, 1000000000);
int findmodp() {
	int le = udle(mtle);
	while (!isp(le))le++;
	return le;
}
using ar = array<int, 2>;


ar ms;
ar ts;

ar rhs[100005];
ar oricnt[100005];
void init() {
	rep(i, 2) {
		ms[i] = findmodp();
		ts[i] = findmodp();
		while (ts[i] % ms[i] == 0) {
			ts[i] = findmodp();
		}
		ts[i] %= ms[i];
	}
	rhs[0] = { 1,1 };
	rep(i, 100005) {
		rep(j, 2) {
			rhs[i + 1][j] = (ll)rhs[i][j] * ts[j] % ms[j];
		}
	}
	oricnt[0] = { 0,0 };
	for (int i = 1; i < 100005; i++) {
		rep(j, 2) {
			oricnt[i][j] = (oricnt[i - 1][j] + rhs[i][j]) % ms[j];
		}
	}
	//cout << ts[0] << " " << ts[1] << "\n";
}
ar operator*(ar a, ll v) {
	rep(j, 2) {
		ll adv = v % ms[j];
		if (adv < 0)adv += ms[j];
		a[j] = (ll)a[j] * adv % ms[j];
	}
	return a;
}
ar operator*(ar a, ar b) {
	rep(j, 2) {
		a[j] = (ll)a[j] * b[j] % ms[j];
	}
	return a;
}
ar operator+(ar a, ar b) {
	rep(j, 2) {
		a[j] += b[j]; if (a[j] >= ms[j])a[j] -= ms[j];
	}
	return a;
}
ar operator-(ar a, ar b) {
	rep(j, 2) {
		a[j] -= b[j]; if (a[j] < 0)a[j] += ms[j];
	}
	return a;
}

int tmp;
struct Data {
	ar val;
	int cnt;
};
Data merge(Data a, Data b) {
	Data res;
	res.val = a.val + b.val * rhs[a.cnt];
	res.cnt = a.cnt + b.cnt;
	return res;
}
Data e = { {0,0},0 };
const int LIM_N = 1900000;
Data node[LIM_N];
int nex[LIM_N][2];
int mem[1 << 17];


void init_seg() {
	mem[0] = 0;
	int sz = (1 << 16);
	rep(i, 2 * sz - 1) {
		node[i] = e;
		rep(j, 2) {
			nex[i][j] = 2 * i + 1 + j;
		}
	}
	tmp = 2 * sz - 1;
}
int add(int x, int k, int l = 0, int r = -1) {
	if (r < 0)r = (1 << 16);
	if (x < l || r <= x)return k;
	if (l == x && x + 1 == r) {
		int c = node[k].cnt;
		c++;
		node[tmp].val = oricnt[c] * x;
		node[tmp].cnt = c;
		int res = tmp;
		tmp++;
		return res;
	}
	else {
		int nl = nex[k][0];
		int nr = nex[k][1];
		int vl = add(x, nl, l, (l + r) / 2);
		int vr = add(x, nr, (l + r) / 2, r);
		node[tmp] = merge(node[vl], node[vr]);
		nex[tmp][0] = vl, nex[tmp][1] = vr;
		int res = tmp;
		tmp++;
		return res;
	}
	return -1;
}
void addval(int x, int num, int k, int l = 0, int r = -1) {
	if (r < 0)r = (1 << 16);
	if (x < l || r <= x)return;
	if (l == x && x + 1 == r) {
		node[k].cnt += num;
		node[k].val = oricnt[node[k].cnt] * x;
	}
	else {
		int nl = nex[k][0];
		int nr = nex[k][1];
		//cout << "? " << k << " " << nl << " " << nr << "\n";
		addval(x, num, nl, l, (l + r) / 2);
		addval(x, num, nr, (l + r) / 2, r);
		node[k] = merge(node[nl], node[nr]);
	}
}
Data query(int len, int k, int l = 0, int r = -1) {
	if (r < 0)r = (1 << 16);
	Data res;
	if (r - l == 1) {
		res.val = oricnt[len] * l;
		res.cnt = len;
	}
	else {
		int vl = nex[k][0];
		int vr = nex[k][1];
		if (node[vr].cnt >= len) {
			res = query(len, vr, (l + r) / 2, r);
		}
		else {
			Data res2 = node[vr];
			Data res1 = query(len - res2.cnt, vl, l, (l + r) / 2);
			res = merge(res1, res2);
		}
	}
	return res;
}
int getcol(int len, int k, int l = 0, int r = -1) {
	if (len == node[k].cnt)return -1;
	if (r < 0)r = (1 << 16);
	int res;
	if (r - l == 1) {
		res = l;
	}
	else {
		int vl = nex[k][0];
		int vr = nex[k][1];
		if (node[vr].cnt > len) {
			res = getcol(len, vr, (l + r) / 2, r);
		}
		else {
			res = getcol(len - node[vr].cnt, vl, l, (l + r) / 2);
		}
	}
	return res;
}


struct edge {
	int to, cost;
};
void solve() {
	init_seg();
	int n, m; cin >> n >> m;
	vector<vector<edge>> G(n);
	rep(i, m) {
		int a, b; cin >> a >> b; a--; b--;
		int c; cin >> c;
		G[a].push_back({ b,c });
		G[b].push_back({ a,c });
	}
	vector<ll> dist(n, INF);
	priority_queue<LP, vector<LP>, greater<LP>> q;
	dist[0] = 0;
	q.push({ 0,0 });
	vector<int> ids;
	while (!q.empty()) {
		LP p = q.top(); q.pop();
		int id = p.second;
		ll d = p.first;
		if (dist[id] < d)continue;
		ids.push_back(id);
		for (edge e : G[id]) {
			ll nd = d + e.cost;
			if (nd < dist[e.to]) {
				dist[e.to] = nd;
				q.push({ nd,e.to });
			}
		}
	}
	//coutarray(dist);
	vector<int> par(n);
	for (int id : ids) {
		if (id == 0)continue;
		vector<edge> pres;
		for (edge e : G[id]) {
			if (dist[e.to] + e.cost == dist[id]) {
				pres.push_back(e);
			}
		}
		//cout << id << " " << pres.size() << "\n";
		edge chk = pres[0];
		for (int i = 1; i < pres.size(); i++) {
			edge e = pres[i];
			int len = min(node[mem[chk.to]].cnt, node[mem[e.to]].cnt) + 1;
			int le = 0, ri = len + 1;
			while (ri - le > 1) {
				int mid = (le + ri) / 2;
				addval(chk.cost, 1, mem[chk.to]);
				Data dl = query(mid, mem[chk.to]);
				addval(chk.cost, -1, mem[chk.to]);
				addval(e.cost, 1, mem[e.to]);
				Data dr = query(mid, mem[e.to]);
				addval(e.cost, -1, mem[e.to]);
				//cout << "? " << id << " " << chk.to << " " << e.to << " " << mid << "\n";
				//rep(j, 2)cout << dl.val[j] << " "; cout << "\n";
				//rep(j, 2)cout << dr.val[j] << " "; cout << "\n";
				if (dl.val == dr.val) {
					le = mid;
				}
				else {
					ri = mid;
				}
			}
			//cout << "? " << id << " " << chk.to << " " << e.to << " " << le << "\n";
			addval(chk.cost, 1, mem[chk.to]);
			int vl = getcol(le, mem[chk.to]);
			addval(chk.cost, -1, mem[chk.to]);
			addval(e.cost, 1, mem[e.to]);
			int vr = getcol(le, mem[e.to]);
			addval(e.cost, -1, mem[e.to]);
			//cout << "? " << id << " " << chk.to << " " << e.to << " " << le << " " << vl << " " << vr << "\n";
			if (vl < vr)chk = e;
		}

		mem[id] = add(chk.cost, mem[chk.to]);
		//cout << id << " " << mem[id] << "\n";
		par[id] = chk.to;
		if (id == n - 1)break;
	}
	vector<int> ans;
	int cur = n - 1;
	while (cur != 0) {
		ans.push_back(cur); cur = par[cur];
	}
	ans.push_back(0);
	reverse(all(ans));
	rep(i, ans.size())ans[i]++;
	cout << ans.size() << "\n";
	coutarray(ans);
}


signed main() {
	ios::sync_with_stdio(false);
	cin.tie(0);
	//cout << fixed << setprecision(10);
	//init_f();
	init();
	//expr();
	//while(true)
	int t; cin >> t; rep(i, t)
		solve();
	return 0;
}