#include <iostream>
#include <cstdio>
#include <cstring>
#include <algorithm>
#include <cmath>
using namespace std;
const int N=2e4+5,M=5e4+5;
typedef long long ll;
inline int read(){
    char c=getchar();int x=0,f=1;
    while(c<‘0‘||c>‘9‘){if(c==‘-‘)f=-1;c=getchar();}
    while(c>=‘0‘&&c<=‘9‘){x=x*10+c-‘0‘;c=getchar();}
    return x*f;
}
int n,m,u,v;
struct edge{
    int v,ne;
}e[M];
int h[N],cnt=0;
inline void ins(int u,int v){
    cnt++;
    e[cnt].v=v;e[cnt].ne=h[u];h[u]=cnt;
}
int dfn[N],low[N],belong[N],dfc,scc;
int st[N],top=0;
void dfs(int u){
    dfn[u]=low[u]=++dfc;
    st[++top]=u;
    for(int i=h[u];i;i=e[i].ne){
        int v=e[i].v;
        if(!dfn[v]){
            dfs(v);
            low[u]=min(low[u],low[v]);
        }else if(!belong[v])
            low[u]=min(low[u],dfn[v]);
    }
    if(low[u]==dfn[u]){
        scc++;
        while(true){
            int x=st[top--];
            belong[x]=scc;
            if(x==u) break;
        }
    }
}
void findSCC(){
    memset(dfn,0,sizeof(dfn));
    memset(belong,0,sizeof(belong));
    memset(low,0,sizeof(low));
    dfc=scc=top=0;
    for(int i=1;i<=n;i++) if(!dfn[i]) dfs(i);
}
int outd[N],ind[N];
void point(){
    memset(ind,0,sizeof(ind));
    memset(outd,0,sizeof(outd));
    for(int u=1;u<=n;u++)
        for(int i=h[u];i;i=e[i].ne){
            int v=e[i].v;
            if(belong[u]!=belong[v]) outd[belong[u]]++,ind[belong[v]]++;
        }
}
int T;
int main(){
    T=read();
    while(T--){
        n=read();m=read();
        cnt=0;
        memset(h,0,sizeof(h));
        for(int i=1;i<=m;i++){u=read();v=read();ins(u,v);}
        findSCC();
        point();
        int cnt1=0,cnt2=0;
        for(int i=1;i<=scc;i++){
            if(ind[i]==0) cnt1++;
            if(outd[i]==0) cnt2++;
        }
        if(scc==1) printf("0\n");
        else printf("%d\n",max(cnt1,cnt2));
    }
}