#include<iostream> #include<cstring> using namespace std; int mapp[2005][2005],color[2005],n; int dfs(int x,int c) { color[x]=c; for(int i=1;i<=n;i++) { if(mapp[x][i]==1) { if(color[i]==c) return 0; if(color[i]==0&&!dfs(i,-c)) return 0; } } return 1; } int main() { int T,m,x,flag,y,g; cin>>T; while(T--) { cin>>n>>m; memset(mapp,0,sizeof(mapp)); memset(color,0,sizeof(color)); for(int i=1;i<=m;i++) { cin>>x>>y; mapp[x][y]=1; mapp[y][x]=1; } flag=0; for(int i=1;i<=n;i++) { if(color[i]==0&&!dfs(i,1)) { flag=1; break; } } if(flag==1) { cout<<"No"<<endl; } else { cout<<"Yes"<<endl; } } }