Untitled

//The Settlers of Catan
#define _CRT_SECURE_NO_WARNINGS
#include<iostream>

using namespace std;
int n , m, front, rear;
int arr[30][30], vs[30][30], d[30][30], queue_i[9000000], kc[30];

void set(){
	for(int i = 0; i < n; i++){
		kc[i] = 0;
		for(int j = 0; j < n; j++){
			vs[i][j] = 0;
		}
	}
}

void Push(int x){
	queue_i[rear] = x;
	rear++;
}

void bfs(int x){
	kc[x] = 1;
	front = 0;
	rear = 0;
	Push(x);
	while(rear != front){
		int y = queue_i[front];
		front++;
		for(int i = 1; i <= d[y][0]; i++){
			if(vs[y][d[y][i]] == 0){
				
				if(!kc[d[y][i]]){
					kc[d[y][i]] = kc[y] + 1;
					vs[y][d[y][i]] = 1;
					vs[d[y][i]][y] = 1;
					Push(d[y][i]);
				}
				else if(kc[d[y][i]] <  kc[y] + 1){
					kc[d[y][i]] = kc[y] + 1;
					vs[y][d[y][i]] = 1;
					vs[d[y][i]][y] = 1;
					Push(d[y][i]);
				}
			}
		}
	}
}

int main(){

	freopen("ip.txt", "r", stdin);
	int T; cin >> T;
	for(int tc = 1; tc <= T; tc++){
		cin >> n >> m;

		for(int i = 0; i < n; i++){
			for(int j = 0; j < n; j++){
				arr[i][j] = 0;
				
				d[i][j] = 0;
			}
		}

		for(int i = 1; i <= m ; i++){
			int x, y;
			cin >> x >> y;
			arr[x][y] = 1;
			arr[y][x] = 1;
		}
		for(int i = 0; i < n; i++){
			int cnt = 1;
			for(int j = 0; j < n; j++){
				if(arr[i][j]==1){
					d[i][cnt] = j;
					cnt++;
				}
			}
			d[i][0] = cnt-1;
		}
		int res = 0;
		for(int i = 0; i < n; i++){
			set();
			bfs(i);
			for(int i = 0; i < n; i++){
				//cout << kc[i] <<endl;
				res = max(res, kc[i]);
			}
		}
	
		cout << res << endl;
	}
	return 0;
}