#include<bits/stdc++.h>
#define lli long long int
using namespace std;
lli mat[1002][1002];
lli visited[10000];
lli color[10000];
lli isbipartaite(lli src,lli n)
{
queue<lli> q;
while(!q.empty())
q.pop();
q.push(src);
color[src]=1;
while(!q.empty())
{
lli x=q.front();
q.pop();
visited[x]=1;
for(lli v=0;v<n;v++)
{
if(mat[x][v]!=0 && color[v]==-1)
{
color[v]=1-color[x];
q.push(v);
}
else if(mat[x][v]!=0 && color[v]==color[x])
return false;
}
}
return true;
}
int main()
{
lli t;
scanf("%lld",&t);
while(t--)
{
lli n,m;
scanf("%lld%lld",&n,&m);
for(lli i=0;i<n;i++)
{
memset(mat[i],n,sizeof(lli));
}
for(lli i=0;i<m;i++)
{
lli a,b;
scanf("%lld%lld",&a,&b);
a--;b--;
mat[a][b]=1;mat[b][a]=1;
}
for(lli i=0;i<n;i++)
{
for(lli j=0;j<n;j++)
{
if(i==j)
{
mat[i][j]=0;
continue;
}
mat[i][j]=!mat[i][j];
}
}
for(lli i=0;i<n;i++)
{
visited[i]=0;
}
lli c=1;
lli flag=1,x;
for(lli i=0;i<n;i++)
color[i]=-1;
for(lli i=0;i<n;i++)
{
if(visited[i]==0)
x=isbipartaite(i,n);
if(x==0)
flag=0;
}
if(flag==0)
printf("NO\n");
else
printf("YES\n");
}
}
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