#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define lll _int128
#define ull unsigned long long
#define PB push_back
#define fi first
#define se second
#define _int _int128
#define fr(i,a,b) for(int i = a ; i <= b ; i++)
#define rp(i,a,b) for(int i = a ; i >= b ; i--)
#define frp(i,a,b) for(int i = 1 ; i < b ; i ++ )
#define re read()
#define db double
#define ld long double
#define lowbit(x) x&(-x) 
#define IOS ios::sync_with_stdio(false); cin.tie(0); cout.tie(0);
const int inf = 0x3f3f3f3f;
const ll N = 2e6+10;
const ll mod = 1e9+7;
inline ll read()
{
	ll x=0,f=0;
	char ch=getchar();
	while (!isdigit(ch))
		f|=(ch =='-'),ch = getchar();
	while (isdigit(ch))
		x=(x<<1)+(x<<3)+(ch^= 48),ch = getchar();
	return f?-x:x;
}
inline void write(ll x)
{
    if(x < 0)
        putchar('-'),x=-x;
    if(x > 9)
        write(x/10);
    putchar(x%10 + 48);
}
inline void W(ll x,char ch)
{
	write(x);
	putchar(ch);
}
ll lcm(int a,int b)
{
	return a*b / __gcd(a,b);
}
struct edge{
	int x,y;
}e[N];
ll h[N];
int d[100005][105];
int w[100005];
int vis[1000005];
int cnt;
int n,m,q;
int ans =0 ;
map<pair<int,int>,int>mp;
inline void slove()
{
	ans = 0;
	cin>>n>>m;
	mp.clear();
	fr(i,1,m)
	{
		int x,y;
		cin>>x>>y;
		if(x==y) continue;
		if(x > y) swap(x,y);
		if( x == y-1 || (x==1&&y==n))
		mp[{x,y}]++;
	}
	if(n==1)
	{
		cout<<0<<endl;
		return;
	}
	fr(i,1,n-1)
	{
		if(!mp[{i,i+1}]) ans++;
	}
	if(mp[{1,n}] && ans!=0) ans--;
	cout<<ans<<endl;
	
}

int main()
{
	
	IOS
//	freopen("input.txt","r",stdin);
//	freopen("output.txt","w",stdout);
    int tcase = 1;
	cin>>tcase;
    while(tcase--)
    {
    	slove();
	}
    return 0;
}