//#pragma comment(linker, "/STACK:1024000000,1024000000")
#include<cstdio>
#include<cstring>
#include<cstdlib>
#include<algorithm>
#include<iostream>
#include<sstream>
#include<cmath>
#include<climits>
#include<string>
#include<map>
#include<queue>
#include<vector>
#include<stack>
#include<set>
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<int,int> pii;
#define pb(a) push(a)
#define INF 0x1f1f1f1f
#define lson idx<<1,l,mid
#define rson idx<<1|1,mid+1,r
#define PI  3.1415926535898
template<class T> T min(const T& a,const T& b,const T& c) {return min(min(a,b),min(a,c));
}
template<class T> T max(const T& a,const T& b,const T& c) {return max(max(a,b),max(a,c));
}
void debug() {
#ifdef ONLINE_JUDGE
#elsefreopen("d:\\in1.txt","r",stdin);freopen("d:\\out1.txt","w",stdout);
#endif
}
int getch() {int ch;while((ch=getchar())!=EOF) {if(ch!=' '&&ch!='\n')return ch;}return EOF;
}
const int maxn=111222;
int pre[maxn],lowlink[maxn],sccno[maxn],scc_cnt,dfs_clock;
int deg[maxn];
vector<int> g[maxn];
stack<int> s;void dfs(int u)
{lowlink[u]=pre[u]=++dfs_clock;s.push(u);for(int i=0;i<g[u].size();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],lowlink[v]);}if(lowlink[u]==pre[u]){scc_cnt++;while(1){int x=s.top();s.pop();sccno[x]=scc_cnt;if(x==u)break;}}
}void find_scc(int n)
{memset(pre,0,sizeof(pre));memset(sccno,0,sizeof(sccno));dfs_clock=scc_cnt=0;for(int i=1;i<=n;i++)if(!pre[i])dfs(i);
}int main()
{int t;scanf("%d",&t);for(int ca=1;ca<=t;ca++){int n,m;scanf("%d%d",&n,&m);for(int i=1;i<=n;i++)g[i].clear();for(int i=1;i<=m;i++){int u,v;scanf("%d%d",&u,&v);g[u].push_back(v);}find_scc(n);memset(deg,0,sizeof(deg));for(int i=1;i<=n;i++){for(int j=0;j<g[i].size();j++){int u=i,v=g[i][j];if(sccno[u]!=sccno[v])deg[sccno[v]]=1;}}int num=0;for(int i=1;i<=scc_cnt;i++)if(!deg[i])num++;printf("%d\n",num);}return 0;
}