#include<stdio.h>
#include<string.h>
#define N 21000
struct node {
int u,v,next;
}bian[N*3];
int head[N],dfn[N],low[N],index,vis[N],stac[N],top,yong,cnt,suo[N],indegree[N],outdegree[N];
void init() {
yong=0;index=0;top=0;cnt=0;
memset(vis,0,sizeof(vis));
memset(head,-1,sizeof(head));
memset(dfn,0,sizeof(dfn));
memset(low,0,sizeof(low));
memset(indegree,0,sizeof(indegree));
memset(outdegree,0,sizeof(outdegree));
}
void addedge(int u,int v) {
bian[yong].u=u;
bian[yong].v=v;
bian[yong].next=head[u];
head[u]=yong++;
}
int Min(int a,int b) {
return a>b?b:a;
}
void tarjan(int u){
dfn[u]=low[u]=++index;
vis[u]=1;
stac[++top]=u;
int i;
for(i=head[u];i!=-1;i=bian[i].next) {
int v=bian[i].v;
if(!dfn[v]) {
tarjan(v);
low[u]=Min(low[u],low[v]);
}
else
if(vis[v])
low[u]=Min(low[u],dfn[v]);
}
if(low[u]==dfn[u]) {
++cnt;
int t;
do{
t=stac[top--];
suo[t]=cnt;
vis[t]=0;
}while(t!=u);
}
}
int main() {
int n,m,i,in,ou,a,b,t;
scanf("%d",&t);
while(t--) {
scanf("%d%d",&n,&m);
if(m==0) {
printf("%d\n",n);
continue;
}
init();
while(m--) {
scanf("%d%d",&a,&b);
addedge(a,b);
}
for(i=1;i<=n;i++)
if(!dfn[i])
tarjan(i);
if(cnt==1) {//剁手
printf("0\n");
continue;
}
for(i=0;i<yong;i++)
if(suo[bian[i].u]!=suo[bian[i].v]) {
indegree[suo[bian[i].v]]++;
outdegree[suo[bian[i].u]]++;
}
in=0;ou=0;
for(i=1;i<=cnt;i++) {
if(indegree[i]==0)
in++;
if(outdegree[i]==0)
ou++;
}
printf("%d\n",in>ou?in:ou);
}
return 0;
}