//#pragma GCC optimize("Ofast", "unroll-loops")
//#pragma GCC target("sse", "sse2", "sse3", "ssse3", "sse4")
#include <bits/stdc++.h>

#define all(a) a.begin(),a.end()
#define len(a) (int)(a.size())
#define mp make_pair
#define pb push_back
#define fir first
#define sec second
#define fi first
#define se second

using namespace std;

typedef pair<int, int> pii;
typedef long long ll;
typedef long double ld;

template<typename T>
inline bool umin(T &a, T b) {
    if (b < a) {
        a = b;
        return true;
    }
    return false;
}

template<typename T>
inline bool umax(T &a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
    return false;
}

#ifdef LOCAL
#define D for (bool _FLAG = true; _FLAG; _FLAG = false)
#define LOG(...) print(#__VA_ARGS__" ::", __VA_ARGS__) << endl
template <class ...Ts> auto &print(Ts ...ts) { return ((cerr << ts << " "), ...); }
#else
#define D while (false)
#define LOG(...)
#endif // LOCAL

const int max_n = -1, inf = 1000111222;

using base = pair<unsigned short, unsigned short>;


inline vector <base> add(vector <base> &a, int x) {
    for (int i = 0; i < len(a); i++) {
        if (a[i].first == x) {
            auto b = a;
            ++b[i].second;
            return b;
        }
    }
    vector <base> new_a(len(a) + 1);
    int cnt = 0;
    for (int i = 0; i < len(a); ) {
        if (a[i].first < x) {
            new_a[cnt++] = {x, 1};
            x = 0;
        }
        else {
            new_a[cnt++] = a[i];
            ++i;
        }
    }
    if (cnt < len(a) + 1) {
        new_a[cnt] = {x, 1};
    }
    return new_a;
}

inline bool check (vector <base> &a, vector <base> &b) { /// b > a
    for (int i = 0; i < min(len(a), len(b)); i++) {
        if (a[i].first < b[i].first) {
            return true;
        }
        if (a[i].first > b[i].first) {
            return false;
        }
        if (a[i].second < b[i].second) {
            return true;
        }
        if (a[i].second > b[i].second) {
            return false;
        }
    }
    return len(a) < len(b);
}

inline void test_case () {
    int n, m;
    cin >> n >> m;
    vector <pair<pii, int> > e(m + m);
    for (int i = 0; i < m; i++) {
        cin >> e[i].first.first >> e[i].first.second >> e[i].second;
        --e[i].first.first;
        --e[i].first.second;
        e[m + i] = {{e[i].first.second, e[i].first.first}, e[i].second};
    }
    m += m;
    sort(all(e));
    vector <int> p(n);
    for (int i = 0, j = 0; i < n; i++) {
        while (j < m && e[j].first.first < i) {
            ++j;
        }
        p[i] = j;
    }
    priority_queue <pii> q;
    vector <int> d(n, inf);
    d[0] = 0;
    q.push({0, 0});
    while (!q.empty()) {
        int v, dist;
        tie(dist, v) = q.top();
        q.pop();
        if (-dist > d[v]) {
            continue;
        }
        for (int i = p[v]; i < m; i++) {
            if (e[i].first.first != v) break;
            int to = e[i].first.second;
            int len = e[i].second;
            if (umin(d[to], d[v] + len)) {
                q.push({-d[to], to});
            }
        }
    }
    vector <int> order(n);
    iota(all(order), 0);
    sort(all(order), [&] (int a, int b) {
        return d[a] > d[b];
    });
    vector <vector <base> > nice(n);
    vector <bool> good(n);
    vector <int> go(n);
    good[n - 1] = true;
    for (int v : order) {
        if (d[v] > d[n - 1]) {
            continue;
        }
        for (int i = p[v]; i < m; i++) {
            if (e[i].first.first != v) {
                break;
            }
            int to = e[i].first.second;
            int len = e[i].second;
            if (d[to] == d[v] + len && good[to]) {
                auto gg = add(nice[to], len);
                if (!good[v]) {
                    good[v] = true;
                    nice[v] = gg;
                    go[v] = to;
                }
                else if (check(nice[v], gg)){
                    nice[v] = gg;
                    go[v] = to;
                }
            }
        }
    }
    vector <int> ans;
    int v = 0;
    while (v != n - 1) {
        ans.pb(v);
        v = go[v];
    }
    ans.pb(n - 1);
    cout << len(ans) << '\n';
    for (auto &i : ans) {
        cout << i + 1 << ' ';
    }
    cout << '\n';
}

int main() {
//    freopen("input.txt", "r", stdin);
//    freopen("output.txt", "w", stdout);

    ios_base::sync_with_stdio(false);
    cin.tie(nullptr);

    int t = 1;
    cin >> t;
    for (int test = 1; test <= t; test++) {
        test_case();
    }
}