#include<bits/stdc++.h>
using namespace std;
inline int read(){
	int res=0;
	char ch=getchar();
	while(ch<'0'||ch>'9')
		ch=getchar();
	while(ch>='0'&&ch<='9'){
		res=(res<<1)+(res<<3)+(ch^'0');
		ch=getchar();
	}
	return res;
}
int T,n,m,num,tot,dfn[100005],low[100005],vis[100005],ans,siz[100005],dp[100005];
vector<int> G[100005];
stack<int> s;
void Tarjan(int u){
	dfn[u]=low[u]=++num;
	s.push(u);
	for(int i=0,len=G[u].size();i<len;++i){
		int v=G[u][i];
		if(!dfn[v]){
			Tarjan(v);
			low[u]=min(low[u],low[v]);
		} else if(!vis[v])
			low[u]=min(low[u],dfn[v]);
	}
	if(low[u]==dfn[u]){
		vis[u]=++tot;
		++siz[tot];
		while(s.top()!=u){
			vis[s.top()]=tot;
			++siz[tot];
			s.pop();
		}
		s.pop();
	}
}
int dfs(int u){
    if(~dp[u])
		return dp[u];
	check[u]=1;
    int add=0;
    for(int i=1;i<=n;i++)
        if(vis[i]==u)
            for(int j=0,len=G[u].size();j<len;++j){
                int v=G[u][j];
                if(u!=vis[v])
               	 	add=max(add,dfs(vis[v]));
            }
    return dp[u]=add+siz[u];
}
int main(){
	T=read();
	while(T--){
		memset(low,0,sizeof(low));
		memset(dfn,0,sizeof(dfn));
		memset(vis,0,sizeof(vis));
		memset(siz,0,sizeof(siz));
		memset(dp,-1,sizeof(dp));
		ans=tot=num=0;
		while(!s.empty())
			s.pop();
		n=read(),m=read();
		for(int i=1;i<=n;++i)
			G[i].clear();
		for(int i=1;i<=m;++i){
			int u=read(),v=read();
			G[u].push_back(v);
		}
		for(int i=1;i<=n;++i)
			if(!dfn[i])
				Tarjan(i);
		for(int i=1;i<=tot;++i)
			ans=max(ans,dfs(i));
		printf("%d\n",ans);
	}
	return 0;
}