#include <iostream>
#include <cstdio>
#include <cstring>
using namespace std;
const int MAXN = 20005;
typedef struct _node
{
int v, next;
}N;
N edge[MAXN * 3];
int dfn[MAXN], low[MAXN], step;
int inS[MAXN], id[MAXN], scc, myS[MAXN], top;
int in[MAXN], out[MAXN], cntEdge, head[MAXN];
void init()
{
cntEdge = step = scc = top = 0;
for(int i = 0; i < MAXN; i++)
{
head[i] = -1;
dfn[i] = low[i] = -1;
id[i] = -1;
in[i] = out[i] = 0;
inS[i] = 0;
}
}
void tarjan(int n)
{
dfn[n] = low[n] = ++step;
myS[top++] = n;
inS[n] = 1;
for(int f = head[n]; f != -1; f = edge[f].next)
{
int son = edge[f].v;
if(dfn[son] == -1)
{
tarjan(son);
low[n] = min(low[n], low[son]);
}
else if(inS[son] != 0)
low[n] = min(low[n], dfn[son]);
}
if(low[n] == dfn[n])
{
int tmp;
do
{
tmp = myS[--top];
inS[tmp] = 0;
id[tmp] = scc;
}while(myS[top] != n);
scc++;
}
}
void addEdge(int u, int v)
{
edge[cntEdge].v = v;
edge[cntEdge].next = head[u];
head[u] = cntEdge++;
}
int main(void)
{
#ifndef ONLINE_JUDGE
freopen("inHDU2767.txt", "r", stdin);
#endif
int n, m, cas;
scanf("%d", &cas);
while(cas--)
{
scanf("%d %d", &n, &m);
init();
int u, v;
for(int i = 0; i < m; i++)
{
scanf("%d %d", &u, &v);
addEdge(u, v);
}
for(int i = 1; i <= n; i++)
{
if(dfn[i] == -1)
tarjan(i);
}
for(int i = 1; i <= n; i++)
{
for(int j = head[i]; j != -1; j = edge[j].next)
{
u = i, v = edge[j].v;
if(id[u] == id[v])
continue;
else
{
in[id[v]]++;
out[id[u]]++;
}
}
}
int inNum = 0, outNum = 0;
for(int i = 0; i < scc; i++)
{
if(!in[i])
inNum++;
if(!out[i])
outNum++;
}
if(scc >= 2)
printf("%d\n", max(inNum, outNum));
else
printf("0\n");
}
return 0;
}