#include<bits/stdc++.h>

using namespace std;

const int maxn = 2e4+;

const int maxm = 5e4+;

int head[maxn],nxt[maxm],to[maxm],ecnt;

void addEdge(int u,int v)

{

    nxt[ecnt] = head[u];

    to[ecnt] = v;

    head[u] = ecnt++;

}

void initGraph(int n)

{

    memset(head,-,sizeof(int)*(n+)); ecnt = ;

}

int sccno[maxn],pre[maxn],low[maxn],dfs_clock,scc_cnt;

stack<int> stk;

void tarjan(int u)

{

    pre[u] = low[u] = ++dfs_clock;

    stk.push(u);

    for(int i = head[u]; ~i; i = nxt[i]){

        int v = to[i];

        if(!pre[v]){

            tarjan(v);

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

        }else if(!sccno[v]){

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

        }

    }

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

        scc_cnt++;

        while(stk.size()){

            int x = stk.top(); stk.pop();

            sccno[x] = scc_cnt;

            if(x == u) break;

        }

    }

}

void find_scc(int n)

{

    memset(pre,,sizeof(int)*(n+));

    memset(sccno,,sizeof(int)*(n+));

    scc_cnt = dfs_clock = ;

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

        if(!pre[i]) tarjan(i);

    }

}

int ind[maxn],outd[maxn];

int main()

{

    //freopen("in.txt","r",stdin);

    int T; scanf("%d",&T);

    while(T--){

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

        initGraph(n);

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

            int u,v; scanf("%d%d",&u,&v);

            addEdge(u-,v-);

        }

        find_scc(n);

        if(scc_cnt == ) {

            printf("0\n"); continue;

        }

        for(int i = ; i <= scc_cnt; i++) ind[i] = outd[i] = ;

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

            for(int i = head[u]; ~i; i = nxt[i]){

                int v = to[i];

                if(sccno[u] != sccno[v]) outd[sccno[u]]++,ind[sccno[v]]++;

            }

        }

        int a = ,b = ;

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

            if(!outd[i]) b++;

            if(!ind[i]) a++;

        }

        printf("%d\n",max(a,b));

    }

    return ;

}