#include <iostream>
#include <vector>
#include <set>
using namespace std;
using vi = vector<int>;

void solve() {
	int n, m; cin >> n >> m;
	vector<set<int, greater<int>>> adj(n+1);
	for (int i = 0; i < m; i++) {
		int u, v; cin >> u >> v;
		adj[u].insert(v);
		adj[v].insert(u);
	}
	vi st;

	st.push_back(1);
	int out = 0;
	while (st.size()) {
		int top = st.back();
		st.pop_back();
		if (top == n) break;
		while (st.size() && st.back() < top) st.pop_back();
		for (int i : adj[top]) {
			if (i > top) {
				st.push_back(i);
			}
		}
		if (st.size() && st.back() == top+1) continue;
		out++;
		st.push_back(top+1);
	}
	cout << out << endl;
}

int main() {
	int t; cin >> t;
	while (t--) solve();
}