#include <cassert>
#include <cmath>
#include <cstdint>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <functional>
#include <iostream>
#include <limits>
#include <map>
#include <numeric>
#include <queue>
#include <random>
#include <set>
#include <sstream>
#include <string>
#include <unordered_map>
#include <unordered_set>
#include <utility>
#include <vector>

using namespace std;

using Int = long long;

template <class T1, class T2> ostream &operator<<(ostream &os, const pair<T1, T2> &a) { return os << "(" << a.first << ", " << a.second << ")"; };
template <class T> ostream &operator<<(ostream &os, const vector<T> &as) { const int sz = as.size(); os << "["; for (int i = 0; i < sz; ++i) { if (i >= 256) { os << ", ..."; break; } if (i > 0) { os << ", "; } os << as[i]; } return os << "]"; }
template <class T> void pv(T a, T b) { for (T i = a; i != b; ++i) cerr << *i << " "; cerr << endl; }
template <class T> bool chmin(T &t, const T &f) { if (t > f) { t = f; return true; } return false; }
template <class T> bool chmax(T &t, const T &f) { if (t < f) { t = f; return true; } return false; }
#define COLOR(s) ("\x1b[" s "m")

////////////////////////////////////////////////////////////////////////////////
template <unsigned M_> struct ModInt {
  static constexpr unsigned M = M_;
  unsigned x;
  constexpr ModInt() : x(0U) {}
  constexpr ModInt(unsigned x_) : x(x_ % M) {}
  constexpr ModInt(unsigned long long x_) : x(x_ % M) {}
  constexpr ModInt(int x_) : x(((x_ %= static_cast<int>(M)) < 0) ? (x_ + static_cast<int>(M)) : x_) {}
  constexpr ModInt(long long x_) : x(((x_ %= static_cast<long long>(M)) < 0) ? (x_ + static_cast<long long>(M)) : x_) {}
  ModInt &operator+=(const ModInt &a) { x = ((x += a.x) >= M) ? (x - M) : x; return *this; }
  ModInt &operator-=(const ModInt &a) { x = ((x -= a.x) >= M) ? (x + M) : x; return *this; }
  ModInt &operator*=(const ModInt &a) { x = (static_cast<unsigned long long>(x) * a.x) % M; return *this; }
  ModInt &operator/=(const ModInt &a) { return (*this *= a.inv()); }
  ModInt pow(long long e) const {
    if (e < 0) return inv().pow(-e);
    ModInt a = *this, b = 1U; for (; e; e >>= 1) { if (e & 1) b *= a; a *= a; } return b;
  }
  ModInt inv() const {
    unsigned a = M, b = x; int y = 0, z = 1;
    for (; b; ) { const unsigned q = a / b; const unsigned c = a - q * b; a = b; b = c; const int w = y - static_cast<int>(q) * z; y = z; z = w; }
    assert(a == 1U); return ModInt(y);
  }
  ModInt operator+() const { return *this; }
  ModInt operator-() const { ModInt a; a.x = x ? (M - x) : 0U; return a; }
  ModInt operator+(const ModInt &a) const { return (ModInt(*this) += a); }
  ModInt operator-(const ModInt &a) const { return (ModInt(*this) -= a); }
  ModInt operator*(const ModInt &a) const { return (ModInt(*this) *= a); }
  ModInt operator/(const ModInt &a) const { return (ModInt(*this) /= a); }
  template <class T> friend ModInt operator+(T a, const ModInt &b) { return (ModInt(a) += b); }
  template <class T> friend ModInt operator-(T a, const ModInt &b) { return (ModInt(a) -= b); }
  template <class T> friend ModInt operator*(T a, const ModInt &b) { return (ModInt(a) *= b); }
  template <class T> friend ModInt operator/(T a, const ModInt &b) { return (ModInt(a) /= b); }
  explicit operator bool() const { return x; }
  bool operator==(const ModInt &a) const { return (x == a.x); }
  bool operator!=(const ModInt &a) const { return (x != a.x); }
  bool operator<(const ModInt &a) const { return (x < a.x); }
  friend std::ostream &operator<<(std::ostream &os, const ModInt &a) { return os << a.x; }
};
////////////////////////////////////////////////////////////////////////////////

constexpr unsigned MO = 1000000007;
using Mint = ModInt<MO>;


int root(vector<int> &uf, int u) {
  return (uf[u] < 0) ? u : (uf[u] = root(uf, uf[u]));
}
bool connect(vector<int> &uf, int u, int v) {
  u = root(uf, u);
  v = root(uf, v);
  if (u == v) return false;
  if (uf[u] > uf[v]) swap(u, v);
  uf[u] += uf[v];
  uf[v] = u;
  return true;
}


int N, M;
vector<pair<int, int>> E;

bool adj(int u, int v) {
  auto it = lower_bound(E.begin(), E.end(), make_pair(u, v));
  return (it != E.end() && *it == make_pair(u, v));
}

vector<vector<int>> graph, hparg;

vector<pair<int, Mint>> ans;

void go(int src) {
  int len = 0;
  Mint key = 0;
  vector<int> vis(N, 0);
  for (int u = src; ; ) {
    (key *= 10) += (u + 1);
    vis[u] = 1;
    if (++len == N) {
      ans.emplace_back(src, key);
      return;
    }
    int vm = -1;
    for (const int v : graph[u]) if (!vis[v]) {
      if (~vm) return;
      vm = v;
    }
    if (!~vm) return;
    u = vm;
  }
}
void og(int snk) {
  int len = 0;
  Mint key = 0, ten = 1;
  vector<int> vis(N, 0);
  for (int u = snk; ; ) {
    key += (u + 1) * ten;
    ten *= 10;
    vis[u] = 1;
    if (++len == N) {
      // OK
      ans.emplace_back(u, key);
      return;
    }
    int vm = -1;
    for (const int v : hparg[u]) if (!vis[v]) {
      if (~vm) return;
      vm = v;
    }
    if (!~vm) return;
    u = vm;
  }
}

int main() {
  for (int numCases; ~scanf("%d", &numCases); ) { for (int caseId = 1; caseId <= numCases; ++caseId) {
    scanf("%d%d", &N, &M);
    E.resize(M);
    for (int i = 0; i < M; ++i) {
      scanf("%d%d", &E[i].first, &E[i].second);
      --E[i].first;
      --E[i].second;
    }
    sort(E.begin(), E.end());
    E.erase(unique(E.begin(), E.end()), E.end());
    M = E.size();
    
    graph.assign(N, {});
    hparg.assign(N, {});
    for (int i = 0; i < M; ++i) {
      const int u = E[i].first, v = E[i].second;
      graph[u].push_back(v);
      hparg[v].push_back(u);
    }
    
    ans.clear();
    // for (int u = 0; u < N; ++u) go(u);
    // for (int u = 0; u < N; ++u) og(u);
    
    vector<int> indeg(N, 0), outdeg(N, 0);
    for (int i = 0; i < M; ++i) {
      const int u = E[i].first, v = E[i].second;
      ++outdeg[u];
      ++indeg[v];
    }
    
    // component: l -> * -> ... * -> r determined
    vector<int> uf(N, -1);
    vector<int> ls(N), rs(N);
    vector<int> nxt(N, -1), prv(N, -1);
    for (int u = 0; u < N; ++u) ls[u] = rs[u] = u;
    auto L = [&](int u) -> int & { return ls[root(uf, u)]; };
    auto R = [&](int u) -> int & { return rs[root(uf, u)]; };
    auto isGood = [&](int u, int v) -> bool {
      return (root(uf, u) != root(uf, v) && R(u) == u && L(v) == v);
    };
    
    queue<int> que;
    auto check = [&](int u) -> void {
      if (indeg[L(u)] >= 2 && outdeg[R(u)] == 1) que.push(R(u));
      if (indeg[L(u)] == 1 && outdeg[R(u)] >= 1) que.push(L(u));
    };
    for (int u = 0; u < N; ++u) {
      if (indeg[u] == 0) { go(u); goto done; }
      if (outdeg[u] == 0) { og(u); goto done; }
      check(u);
    }
    for (; que.size(); ) {
      const int u = que.front();
      que.pop();
      if (indeg[L(u)] >= 2 && outdeg[R(u)] == 1 && R(u) == u) {
        for (const int v : graph[u]) if (isGood(u, v)) {
// cerr<<__LINE__<<"> u="<<u<<" -> v="<<v<<endl;
          for (const int w : hparg[v]) if (u != w && isGood(w, v)) {
            --outdeg[w];
            check(w);
          }
          const int l = L(u), r = R(v);
          connect(uf, u, v);
          L(u) = l; R(u) = r;
          nxt[u] = v; prv[v] = u;
          break;
        }
        assert(R(u) != u);
      } else if (indeg[L(u)] == 1 && outdeg[R(u)] >= 2 && L(u) == u) {
        for (const int v : hparg[u]) if (isGood(v, u)) {
// cerr<<__LINE__<<"> v="<<v<<" -> u="<<u<<endl;
          for (const int w : graph[v]) if (u != w && isGood(v, w)) {
            --outdeg[w];
            check(w);
          }
          const int l = L(v), r = R(u);
          connect(uf, v, u);
          L(u) = l; R(u) = r;
          nxt[v] = u; prv[u] = v;
          break;
        }
        assert(L(u) != u);
      } else {
        continue;
      }
      // useless edge
      if (adj(R(u), L(u))) {
        --outdeg[R(u)];
        --indeg[L(u)];
      }
      check(u);
    }
    
    for (int u = 0; u < N; ++u) if (R(u) == u) {
      // (>= 2 such components ==> impossible)
      if (indeg[L(u)] >= 2 && outdeg[R(u)] >= 2) {
        int cnt = 0;
        // >= 3 such v ==> impossible
        for (const int v : graph[u]) if (isGood(u, v)) {
// cerr<<__LINE__<<"> "<<u<<" "<<v<<endl;
          go(v);
          if (++cnt == 2) break;
        }
        goto done;
      }
    }
    
    // a Hamiltonian cycle left
    {
// cerr<<__LINE__<<"> nxt = "<<nxt<<", prv = "<<prv<<endl;
      for (int i = 0; i < M; ++i) {
        const int u = E[i].first, v = E[i].second;
        if (isGood(u, v)) {
          nxt[u] = v;
          prv[v] = u;
        }
      }
      vector<int> us;
      for (int u = 0; ; ) {
        us.push_back(u);
        if ((u = nxt[u]) == 0) break;
      }
// cerr<<__LINE__<<"> us = "<<us<<endl;
      assert((int)us.size() == N);
      vector<int> su(N, -1);
      for (int j = 0; j < N; ++j) su[us[j]] = j;
      vector<int> fs(N + 1, 0);
      for (int i = 0; i < M; ++i) {
        const int u = E[i].first, v = E[i].second;
        if ((su[u] + 1) % N != su[v]) {
          // bad: (su[v], su[u]]
          if (su[v] < su[u]) {
            ++fs[su[v] + 1];
            --fs[su[u] + 1];
          } else {
            ++fs[su[v] + 1];
            --fs[N];
            ++fs[0];
            --fs[su[u] + 1];
          }
        }
      }
      for (int j = 0; j < N; ++j) fs[j + 1] += fs[j];
// cerr<<__LINE__<<"> fs = "<<fs<<endl;
      const Mint ten = Mint(10).pow(N - 1);
      Mint key = 0;
      for (int j = 0; j < N; ++j) (key *= 10) += (us[j] + 1);
      for (int j = 0; j < N; ++j) {
        if (!fs[j]) {
          ans.emplace_back(us[j], key);
        }
        key -= (us[j] + 1) * ten;
        key *= 10;
        key += (us[j] + 1);
      }
    }
    
   done:{}
#ifdef LOCAL
cerr<<"ans = "<<ans<<endl;
#endif
    sort(ans.begin(), ans.end());
    printf("%d\n", (int)ans.size());
    if (ans.size()) {
      for (int i = 0; i < (int)ans.size(); ++i) {
        if (i) printf(" ");
        printf("%u", ans[i].second.x);
      }
      puts("");
    }
  }
#ifndef LOCAL
  break;
#endif
  }
  return 0;
}