#include<cstdio>

 #include<cstring>

 #include<algorithm>

 using namespace std;

 #define MAXN 1111

 #define MAXM 55000

 struct Edge{

     int u,v,next;

 }edge[MAXM];

 int NE,head[MAXN];

 void addEdge(int u,int v){

     edge[NE].u=u; edge[NE].v=v; edge[NE].next=head[u];

     head[u]=NE++;

 }

 int top,stack[MAXN];

 bool instack[MAXN];

 int dn,dfn[MAXN],low[MAXN];

 int bn,belong[MAXN],size[MAXN];

 void tarjan(int u){

     dfn[u]=low[u]=++dn;

     stack[++top]=u; instack[u]=;

     for(int i=head[u]; i!=-; i=edge[i].next){

         int v=edge[i].v;

         if(dfn[v]==){

             tarjan(v);

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

         }else if(instack[v]){

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

         }

     }

     if(low[u]==dfn[u]){

         int v; ++bn;

         do{

             v=stack[top--];

             instack[v]=;

             belong[v]=bn;

             ++size[bn];

         }while(u!=v);

     }

 }

 int d[MAXN];

 int dfs(int u){

     if(d[u]) return d[u];

     int res=;

     for(int i=head[u]; i!=-; i=edge[i].next){

         int v=edge[i].v;

         res=max(res,dfs(v));

     }

     return d[u]=res+size[u];

 }

 int main(){

     int t,n,m,a,b;

     scanf("%d",&t);

     while(t--){

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

         NE=;

         memset(head,-,sizeof(head));

         while(m--){

             scanf("%d%d",&a,&b);

             addEdge(a,b);

         }

         top=dn=bn=;

         memset(dfn,,sizeof(dfn));

         memset(instack,,sizeof(instack));

         memset(size,,sizeof(size));

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

             if(dfn[i]==) tarjan(i);

         }

         int tmp=NE; NE=;

         memset(head,-,sizeof(head));

         for(int i=; i<tmp; ++i){

             int u=belong[edge[i].u],v=belong[edge[i].v];

             if(u==v) continue;

             addEdge(u,v);

         }

         memset(d,,sizeof(d));

         int res=;

         for(int i=; i<=bn; ++i){

             res=max(res,dfs(i));

         }

         printf("%d\n",res);

     }

     return ;

 }