#include<cstdio>

 #include<vector>

 #include<cstring>

 #include<algorithm>

 #include<stack>

 #define maxn 50005

 using namespace std;

 vector<int>ve[maxn];

 int dfn[maxn],low[maxn],ans,n,m,nncount,b[maxn];

 int from[maxn],to[maxn],cntin[maxn],cntout[maxn];

 bool instack[maxn];

 stack<int>q;

 void tarjin(int x)

 {

     dfn[x]=low[x]=++nncount;

     instack[x]=;

     q.push(x);

     int l=ve[x].size();

     for(int i=; i<l; i++)

     {

         int v=ve[x][i];

         if(!dfn[v])

         {

             tarjin(v);

             low[x]=min(low[x],low[v]);

         }

         else if(instack[v])

             low[x]=min(low[x],dfn[v]);

     }

     if(low[x]==dfn[x])

     {

         ans++;

         int v;

         do

         {

             v=q.top();

             q.pop();

             b[v]=ans;

             instack[v]=;

         }while(v!=x);

     }

 }

 int main()

 {

     int x,y,t,mm1,mm2;

     scanf("%d",&t);

     while(t--)

     {

         memset(cntin,,sizeof cntin);

         memset(cntout,,sizeof cntout);

         memset(b,,sizeof b);

         memset(dfn,,sizeof dfn);

         memset(low,,sizeof low);

         scanf("%d%d",&n,&m);

         for(int i=; i<=n; i++)

         {

             ve[i].clear();

             instack[i]=;

         }

         while(!q.empty()) q.pop();

         for(int i=; i<=m; i++)

         {

             scanf("%d%d",&x,&y);

             ve[x].push_back(y);

             from[i]=x,to[i]=y;

         }

         nncount=ans=mm1=mm2=;

         for(int i=; i<=n; i++)

             if(!dfn[i]) tarjin(i);

         if(ans==){printf("0\n");continue;}

         for(int i=;i<=m;i++)

         {

             x=b[from[i]],y=b[to[i]];

             if(x!=y) cntout[x]++,cntin[y]++;

         }

         for(int i=;i<=ans;i++)

         {

             if(!cntin[i]) mm1++;

             if(!cntout[i]) mm2++;

         }

         printf("%d\n",max(mm1,mm2));

     }

     return ;

 }