int main()
{
int runs, n, m;
scanf("%d", &runs);
while (runs--) {
nA = 0;
memset(V, 0, sizeof(V));
scanf("%d%d", &n, &m);
for (int i = 0, a, b; i < m; ++i) {
scanf("%d%d", &a, &b);
addArc(a, b);
}
init_tarjan();
for (int i = 1; i <= n; ++i) {
if (vis[i] == 0) {
tarjan(i);
}
}
memset(mat, 0, sizeof(mat));
memset(ind, 0, sizeof(ind));
for (int i = 1; i <= n; ++i) {
for (Arc *a = V[i]; a; a = a->next) {
int u = id[i], v = id[a->to];
if (u != v && false == mat[u][v]) {
mat[u][v] = true;
++ind[v];
}
}
}
// top sort
top = -1;
for (int i = 0; i < sc_cnt; ++i) {
if (ind[i] == 0) vstack[++top] = i;
}
int cnt = 0;
while (cnt < sc_cnt) {
int u = vstack[top--];
ord[cnt++] = u;
for (int v = 0; v < sc_cnt; ++v) {
if (mat[u][v]) {
--ind[v];
if (ind[v] == 0) vstack[++top] = v;
}
}
}
bool ans = true;
for (int i = 0; i < cnt-1; ++i) {
if (false == mat[ord[i]][ord[i+1]]) {
ans = false;
break;
}
}
puts(ans ? "Yes" : "No");
}
return 0;
}
int tarjan(int n){
init_tarjan();
for(int i=0;i<n;i++){
if(!pre[i]) dfs(i);
}
for(int i=0;i<n;i+=2){
// printf("%d %d\n",subid[i],subid[i^1]);
if(subid[i]==subid[i^1]) return 0;
}
return 1;
}