#include <bits/stdc++.h>
using namespace std;
const int MAXN = 1e5 + 5;

int DFN[MAXN], LOW[MAXN], sccno[MAXN], dfs_clock, scc_cnt;
stack<int> S;
vector<int> G[MAXN];
void init(int n){ for (int i = 0; i <= n; i++) G[i].clear(); }
void dfs(int u)
{
    DFN[u] = LOW[u] = ++dfs_clock;
 

    S.push(u);
    for (int i = 0; i < G[u].size(); i++)
    {
        int v = G[u][i];
        if (!DFN[v])
        {
            dfs(v);
            LOW[u] = min(LOW[u], LOW[v]);
        }
        else if (!sccno[v])
            LOW[u] = min(LOW[u], DFN[v]);
    }
    if (LOW[u] == DFN[u])
    {
 

        scc_cnt++;
        while (1)
        {
            int x = S.top();
            S.pop();
            sccno[x] = scc_cnt;
            if (x == u)
                break;
        }
    }
}
void find_scc(int n)
{
    dfs_clock= scc_cnt  = 0;
    memset(DFN, 0, sizeof(DFN)), memset(sccno, 0, sizeof
 
(sccno));
    for (int i = 0; i < n; i++)
        if (!DFN[i]) dfs(i);
}

int n, m, in0[MAXN], out0[MAXN];
int main()
{
    int T; scanf("%d", &T);
    while (T--)
    {
        scanf("%d%d", &n, &m);
        init(n);
        for (int i = 0; i < m; i++)
        {
            int u, v;
            scanf("%d%d", &u, &v); u--, v--;
            G[u].push_back(v);
        }
        find_scc(n);
        for (int i = 1; i <= scc_cnt; i++) in0[i] = out0[i] = 0;
        for (int u = 0; u < n; u++)
        {
            for (int i = 0; i < G[u].size(); i++)
            {
                int v = G[u][i];
                if (sccno[u] != sccno[v]) in0[sccno[v]]++, out0[sccno[u]]++;
            }
        }
        int cnt1 = 0, cnt2 = 0;
        for (int i = 1; i <= scc_cnt; i++)
        {
            if (!in0[i]) cnt1++;
            if (!out0[i]) cnt2++;
        }
        int ans = max(cnt1, cnt2);
        if (scc_cnt == 1) ans = 0;
        printf("%d\n", ans);
    }
    return 0;
}
/*
2
4 0
3 2
1 2
1 3
*/