#include <cstdio>
#include <stack>
#include <set>
#include <iostream>
#include <string>
#include <vector>
#include <queue>
#include <functional>
#include <cstring>
#include <algorithm>
#include <cctype>
#include <ctime>
#include <string>
#include <map>
#include <iomanip>
#include <cmath>
#define LL long long
#define ULL unsigned long long
#define SZ(x) (int)x.size()
#define Lowbit(x) ((x) & (-x))
#define MP(a, b) make_pair(a, b)
#define MS(arr, num) memset(arr, num, sizeof(arr))
#define PB push_back
#define F first
#define S second
#define ROP freopen("input.txt", "r", stdin);
#define MID(a, b) (a + ((b - a) >> 1))
#define LC rt << 1, l, mid
#define RC rt << 1|1, mid + 1, r
#define LRT rt << 1
#define RRT rt << 1|1
#define BitCount(x) __builtin_popcount(x)
#define BitCountll(x) __builtin_popcountll(x)
#define LeftPos(x) 32 - __builtin_clz(x) - 1
#define LeftPosll(x) 64 - __builtin_clzll(x) - 1
const double PI = acos(-1.0);
const int INF = 0x3f3f3f3f;
using namespace std;
const double eps = 1e-6;
const int MAXN = 2e4 + 10;
const int MOD = 1000007;
const int dir[][2] = { {1, 0}, {-1, 0}, {0, -1}, {0, 1} };
 
int dfs_clock, scc_cnt, pre[MAXN], lowlink[MAXN], sccno[MAXN], in[MAXN], out[MAXN];
vector<int> G[MAXN];
stack<int> st;
 
void DFS(int u)
{
    pre[u] = lowlink[u] = ++dfs_clock;
    st.push(u);
    for (int i = 0; i < SZ(G[u]); i++)
    {
        int v = G[u][i];
        if (!pre[v])
        {
            DFS(v);
            lowlink[u] = min(lowlink[u], lowlink[v]);
        }
        else if (!sccno[v]) lowlink[u] = min(lowlink[u], pre[v]);
    }
    if (lowlink[u] == pre[u])
    {
        scc_cnt++;
        while (1)
        {
            int x = st.top(); st.pop();
            sccno[x] = scc_cnt;
            if (x == u) break;
        }
    }
}
 
void FindSCC(int v)
{
    MS(pre, 0); MS(lowlink, 0); MS(sccno, 0);
    dfs_clock = scc_cnt = 0;
    for (int i = 1; i <= v; i++)
        if (!pre[i]) DFS(i);
}
 
int main()
{
   // ROP;
    int T, i, j;
    scanf("%d", &T);
    while (T--)
    {
        MS(in, 0); MS(out, 0);
        int v, e;
        scanf("%d%d", &v, &e);
        for (i = 0; i <= v; i++) G[i].clear();
        for (i = 0; i < e; i++)
        {
            int a, b;
            scanf("%d%d", &a, &b);
            G[a].PB(b);
        }
        FindSCC(v);
        if (scc_cnt == 1)
        {
            puts("0");
            continue;
        }
        for (i = 1; i <= v; i++)
        {
            for (j = 0; j < SZ(G[i]); j++)
            {
                if (sccno[i] != sccno[G[i][j]])
                {
                    out[sccno[i]]++;
                    in[sccno[G[i][j]]]++;
                }
            }
        }
        int inAns = 0, outAns = 0;
        for (i = 1; i <= scc_cnt; i++)
        {
            if (in[i] == 0) inAns++;
            if (out[i] == 0) outAns++;
        }
        printf("%d\n", max(inAns, outAns));
    }
    return 0;
}