#include<cstdio>
#include<iostream>
#include<algorithm>
#include<cstring>
#include<cmath>
#include<stack>
#include<vector>
using namespace std;
#define mem(x,y) memset(x,y,sizeof(x))
const int INF=0x3f3f3f3f;
const double PI=acos(-1.0);
const int MAXN=20010;
int scc,dfs_blocks;
int dfn[MAXN],low[MAXN],Instack[MAXN],in[MAXN],out[MAXN],sc[MAXN];
stack<int>S;
vector<int>vec[MAXN];
void initial(){
    scc=0;dfs_blocks=0;
    mem(dfn,0);mem(low,0);mem(Instack,0);mem(in,0);mem(out,0);mem(sc,0);
    while(!S.empty())S.pop();
    for(int i=0;i<MAXN;i++)vec[i].clear();
}
void targin(int u,int fa){
    S.push(u);
    Instack[u]=1;
    dfn[u]=low[u]=++dfs_blocks;
    for(int i=0;i<vec[u].size();i++){
        int v=vec[u][i];
        if(!dfn[v]){
            targin(v,u);
            low[u]=min(low[u],low[v]);
        }
        else if(Instack[v]){
            low[u]=min(low[u],dfn[v]);
        }
    }
    if(low[u]==dfn[u]){
        scc++;
        while(1){
            int v=S.top();
            S.pop();
            Instack[v]=0;
            sc[v]=scc;
            if(u==v)break;
        }
    }
}
int main(){
    int T,m,n,x,y;
    scanf("%d",&T);
    while(T--){
        initial();
        scanf("%d%d",&n,&m);
        while(m--){
            scanf("%d%d",&x,&y);
            vec[x].push_back(y);
        }
        for(int i=1;i<=n;i++){
            if(!dfn[i])targin(i,-1);
        }
        for(int i=1;i<=n;i++){
            for(int j=0;j<vec[i].size();j++){
                int v=vec[i][j];
                if(sc[i]!=sc[v])in[sc[v]]++,out[sc[i]]++;
            }
        }
        int sumin=0,summa=0;
    //    printf("%d\n",scc);
    if(scc==1){
        puts("0");continue;
    }
        for(int i=1;i<=scc;i++){
            if(in[i]==0)sumin++;
            if(out[i]==0)summa++;
            
        }
        printf("%d\n",max(sumin,summa));
    }
    return 0;
}