#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")


// gg: bipartite graph between {vertex} and {biconnected component}
//   (|gg| - n) biconnected components
//   isolated point: not regarded as biconnected component (==> isolated in gg)
// f: DFS out-forest
// ess: edges in biconnected component
//   (u, v) with dis[u] <= dis[v]
//   self-loop at isolated point: not included in ess
struct Biconnected {
  int n, m;
  vector<vector<int>> g, f, gg;
  vector<vector<pair<int, int>>> ess;
  vector<int> par, rs;
  int zeit;
  vector<int> dis, fin, low;

  Biconnected() {}
  explicit Biconnected(int n_) : n(n_), m(0), g(n_) {}
  void ae(int u, int v) {
    ++m;
    assert(0 <= u); assert(u < n);
    assert(0 <= v); assert(v < n);
    g[u].push_back(v);
    if (u != v) g[v].push_back(u);
  }

  int stackVLen, stackELen;
  vector<int> stackV;
  vector<pair<int, int>> stackE;
  vector<int> cntPar;
  void dfs(int u) {
    stackV[stackVLen++] = u;
    dis[u] = low[u] = zeit++;
    for (const int v : g[u]) {
      if (par[u] == v && !cntPar[u]++) continue;
      if (~dis[v]) {
        if (dis[u] >= dis[v]) stackE[stackELen++] = std::make_pair(v, u);
        if (low[u] > dis[v]) low[u] = dis[v];
      } else {
        f[u].push_back(v);
        par[v] = u;
        rs[v] = rs[u];
        const int stackEPos = stackELen;
        stackE[stackELen++] = std::make_pair(u, v);
        dfs(v);
        if (low[u] > low[v]) low[u] = low[v];
        if (dis[u] <= low[v]) {
          const int x = gg.size();
          gg.emplace_back();
          ess.emplace_back();
          for (; ; ) {
            const int w = stackV[--stackVLen];
            gg[w].push_back(x);
            gg[x].push_back(w);
            if (w == v) break;
          }
          gg[u].push_back(x);
          gg[x].push_back(u);
          for (; stackELen > stackEPos; ) ess[x].push_back(stackE[--stackELen]);
        }
      }
    }
    fin[u] = zeit;
  }
  void build() {
    f.assign(n, {});
    gg.assign(n, {});
    ess.assign(n, {});
    par.assign(n, -1);
    rs.assign(n, -1);
    zeit = 0;
    dis.assign(n, -1);
    fin.assign(n, -1);
    low.assign(n, -1);
    stackV.resize(n);
    stackE.resize(m);
    cntPar.assign(n, 0);
    for (int u = 0; u < n; ++u) if (!~dis[u]) {
      stackVLen = stackELen = 0;
      rs[u] = u;
      dfs(u);
    }
  }

  // Returns true iff u is an articulation point
  //   <=> # of connected components increases when u is removed.
  inline bool isArt(int u) const {
    return (gg[u].size() >= 2);
  }

  // Returns w s.t. w is a child of u and a descendant of v in the DFS forest.
  // Returns -1 instead if v is not a proper descendant of u
  //   O(log(deg(u))) time
  int dive(int u, int v) const {
    if (dis[u] < dis[v] && dis[v] < fin[u]) {
      int j0 = 0, j1 = f[u].size();
      for (; j0 + 1 < j1; ) {
        const int j = (j0 + j1) / 2;
        ((dis[f[u][j]] <= dis[v]) ? j0 : j1) = j;
      }
      return f[u][j0];
    } else {
      return -1;
    }
  }
  // Returns true iff there exists a v-w path when u is removed.
  //   O(log(deg(u))) time
  bool isStillReachable(int u, int v, int w) const {
    assert(0 <= u); assert(u < n);
    assert(0 <= v); assert(v < n);
    assert(0 <= w); assert(w < n);
    assert(u != v);
    assert(u != w);
    if (rs[v] != rs[w]) return false;
    if (rs[u] != rs[v]) return true;
    const int vv = dive(u, v);
    const int ww = dive(u, w);
    if (~vv) {
      if (~ww) {
        return (vv == ww || (dis[u] > low[vv] && dis[u] > low[ww]));
      } else {
        return (dis[u] > low[vv]);
      }
    } else {
      if (~ww) {
        return (dis[u] > low[ww]);
      } else {
        return true;
      }
    }
  }
};

////////////////////////////////////////////////////////////////////////////////


vector<int> uf;
int root(int u) {
  return (uf[u] < 0) ? u : (uf[u] = root(uf[u]));
}
bool connect(int u, int v) {
  u = root(u);
  v = root(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<int> A, B;

bool solve() {
  Biconnected bic(N);
  for (int i = 0; i < M; ++i) {
    bic.ae(A[i], B[i]);
  }
  bic.build();
  uf.assign(N << 1, -1);
  for (int x = N; x < (int)bic.gg.size(); ++x) {
    const auto &us = bic.gg[x];
    const auto &es = bic.ess[x];
    if (us.size() == 1) {
      continue;
    }
    for (const int u : us) {
      uf[u << 1] = -1;
      uf[u << 1 | 1] = -1;
    }
    for (const auto &e : es) {
      const int u = e.first;
      const int v = e.second;
      connect(u << 1, v << 1 | 1);
      connect(v << 1, u << 1 | 1);
    }
    int sz[2] = {};
    for (const int u : us) {
      ++sz[(root(us[0] << 1) != root(u << 1)) ? 1 : 0];
    }
    if (!(sz[0] == 2 || sz[1] == 2)) {
      return false;
    }
    if ((int)es.size() != sz[0] * sz[1]) {
      return false;
    }
  }
  return true;
}

int main() {
  for (int numCases; ~scanf("%d", &numCases); ) { for (int caseId = 1; caseId <= numCases; ++caseId) {
    scanf("%d%d", &N, &M);
    A.resize(M);
    B.resize(M);
    for (int i = 0; i < M; ++i) {
      scanf("%d%d", &A[i], &B[i]);
      --A[i];
      --B[i];
    }
    
    const bool ans = solve();
    puts(ans ? "YES" : "NO");
  }
#ifndef LOCAL
  break;
#endif
  }
  return 0;
}