#include<cstdio>
#include<cstring>
#include<iostream>
using namespace std;
const int MAXN=200010;
const int MAXM=500010;
int tot=0;
struct e{
int u,v,w;
int nxt;
}edge[MAXM];
int N,M;
int head[MAXN],low[MAXN],dfn[MAXN],Stack[MAXN];
int Index,Belong[MAXN],degin[MAXN],degout[MAXN],num[MAXN];
bool Instack[MAXN];
int scc,top;
void init(){
tot=0;
memset(head,-1,sizeof(head));
}
void add(int u,int v,int w){
edge[tot].u=u;
edge[tot].v=v;
edge[tot].w=w;
edge[tot].nxt=head[u];
head[u]=tot++;
}
void tarjian(int u)
{
int v;
low[u]=dfn[u]=++Index;
// printf("low[%d]=%d\n",u,low[u]);
// printf("dfn[%d]=%d\n",u,dfn[u]);
Stack[top++]=u;
Instack[u]=true;
for (int i=head[u];i!=-1;i=edge[i].nxt)
{
int v=edge[i].v;
if (!dfn[v])
{
tarjian(v);
if (low[u]>low[v]) low[u]=low[v];
}
else if (Instack[v]&&low[u]>dfn[v])
low[u]=dfn[v];
}
if (low[u]==dfn[u])
{
scc++;
do {
v=Stack[--top];
Instack[v]=false;
Belong[v]=scc;
num[scc]++;
}
while(v!=u);
}
}
void deal(){
memset(dfn,0,sizeof(dfn));
memset(Instack,false,sizeof(Instack));
top=Index=scc=0;
memset(num,0,sizeof(num));
memset(degin,0,sizeof(degin));
memset(degout,0,sizeof(degout));
for (int i=1;i<=N;i++)
{
if (!dfn[i]) tarjian(i);
}
if (scc==1)
{
puts("0");
return;
}
int ret1=0,ret2=0;
for (int i=0;i<tot;i++)
{
int v=Belong[edge[i].v];
int u=Belong[edge[i].u];
if (u==v) continue;
degin[v]++;
degout[u]++;
}
for (int i=1;i<=scc;i++)
{
if (degin[i]==0) ret1++;
if (degout[i]==0) ret2++;
}
printf("%d\n",max(ret1,ret2));
}
int main(){
int T;
scanf("%d",&T);
while (T--){
scanf("%d%d",&N,&M);
init();
for (int i=0;i<M;i++)
{
int u,v;
scanf("%d%d",&u,&v);
add(u,v,9797);
}
deal();
}
return 0;
}
