package com.thealgorithms.datastructures.graphs;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.Arrays;
public final class BipartiteGraphDFS {
private BipartiteGraphDFS() {
}
private static boolean bipartite(int v, ArrayList<ArrayList<Integer>> adj, int[] color, int node) {
if (color[node] == -1) {
color[node] = 1;
}
for (Integer it : adj.get(node)) {
if (color[it] == -1) {
color[it] = 1 - color[node];
if (!bipartite(v, adj, color, it)) {
return false;
}
} else if (color[it] == color[node]) {
return false;
}
}
return true;
}
public static boolean isBipartite(int v, ArrayList<ArrayList<Integer>> adj) {
int[] color = new int[v + 1];
Arrays.fill(color, -1);
for (int i = 0; i < v; i++) {
if (color[i] == -1) {
if (!bipartite(v, adj, color, i)) {
return false;
}
}
}
return true;
}
public static void main(String[] args) throws IOException {
BufferedReader read = new BufferedReader(new InputStreamReader(System.in));
int t = Integer.parseInt(read.readLine().trim());
while (t-- > 0) {
String[] str1 = read.readLine().trim().split(" ");
int numVertices = Integer.parseInt(str1[0]);
int numEdges = Integer.parseInt(str1[1]);
ArrayList<ArrayList<Integer>> adj = new ArrayList<>();
for (int i = 0; i < numVertices; i++) {
adj.add(new ArrayList<>());
}
for (int i = 0; i < numEdges; i++) {
String[] str2 = read.readLine().trim().split(" ");
int vertexU = Integer.parseInt(str2[0]);
int vertexV = Integer.parseInt(str2[1]);
adj.get(vertexU).add(vertexV);
adj.get(vertexV).add(vertexU);
}
boolean ans = isBipartite(numVertices, adj);
if (ans) {
System.out.println("YES");
} else {
System.out.println("NO");
}
}
}
}