#include<bits/stdc++.h>
using namespace std;
int n,T,m,index,team_num;
int low[20005],dfn[20005],team[20005],in[20005],out[20005];
bool instack[20005];
vector<int> mp[20005];
stack<int> S;
void Tarjan ( int u )
{
    dfn[u]=low[u]=++index;
    S.push(u);
    instack[u]=1;
    for ( int i=0;i<mp[u].size();i++)
    {
        int v=mp[u][i];
        if (!dfn[v])
        {
            Tarjan (v) ;
            low[u]=min(low[u],low[v]);
        }
        else if (instack[v]) low[u]=min(low[u],dfn[v]);//是否在栈中
    }
    if (dfn[u]==low[u])  //构成强连通分量
    {
        team_num++; //组数
        while (1)   //同一组标号
        {
            int v=S.top(); S.pop();
            instack[v]=0;
            team[v]=team_num;
            if (v==u) break;
        }
    }
}

void dfs()
{
    memset(team,0,sizeof(team));
    memset(dfn,0,sizeof(dfn));
    memset(low,0,sizeof(low));
    memset(instack,0,sizeof(instack));
    team_num=0;
    index=0;
    for(int i=1;i<=n;i++)
        if (!dfn[i]) Tarjan(i);
}

int main()
{
    scanf("%d",&T);
    while(T--)
    {
        scanf("%d%d",&n,&m);
        for(int i=1;i<=n;i++) mp[i].clear();
        for(int i=1;i<=m;i++)
        {
            int x,y;
            scanf("%d%d",&x,&y);
            mp[x].push_back(y);
        }
        dfs(); //缩点
        /*for(int i=1;i<=n;i++)
            printf("%d:%d\n",i,team[i]);*/

       for(int i=1;i<=team_num;i++) in[i]=out[i]=0;
       for(int i=1;i<=n;i++)
        for(int j=0;j<mp[i].size();j++)
        {
             if (team[i]!=team[mp[i][j]])
             {
                 out[ team[i] ]++;
                 in[ team[mp[i][j]] ]++;
             }
        }
        int innum=0,outnum=0;
        for(int i=1;i<=team_num;i++)
        {
           if (!in[i]) innum++;
           if (!out[i]) outnum++;
        }
        if (team_num==1) printf("0\n");
          else printf("%d\n",max(innum,outnum));
    }
    return 0;
}