#include <bits/stdc++.h>
using namespace std;
//#include "testlib.h"
#define ff first
#define ss second
#define all(v) v.begin(),v.end()
#define int long long
#define ll long long
#define M 1000000007
#define MM 998244353
#define inputarr(a,n) for(int i=0;i<n;++i) cin>>a[i]
#define GCD(m,n) __gcd(m,n)
#define LCM(m,n) m*(n/GCD(m,n))
#define mii  map<ll ,ll >
#define msi  map<string,ll >
#define rep(a,b)    for(ll i=a;i<b;i++)
#define rep0(n)    for(ll i=0;i<n;i++)
#define repi(i,a,b) for(ll i=a;i<b;i++)
#define pb push_back
#define vi vector<ll>
#define vs vector<string>
#define ppb pop_back
#define endl '\n'
#define asdf ios_base::sync_with_stdio(false);cin.tie(0);cout.tie(0);
#define r0 return 0;
#define FORD(i, a, b) for (int i = (int) (a); i >= (int) (b); --i)
#define inputoutput freopen("input.txt", "r", stdin);freopen("output.txt", "w", stdout);
#define Set(a, s) (a, s, sizeof (a))
#define FOR repi
#define vii vector<pii>
#define pii pair<int,int>
#define REVERSE(v) reverse(all(v))
#define trav(a, x) for(auto& a : x)
#define display(x) trav(a,x) cout<<a<<" ";cout<<endl
#define debug cerr<<"bhau"<<endl
#define trace(...) __f(#__VA_ARGS__, __VA_ARGS__)
template <typename Arg1>
void __f(const char* name, Arg1&& arg1){
    std::cerr << name << " : " << arg1 << endl;
}
template <typename Arg1, typename... Args>
void __f(const char* names, Arg1&& arg1, Args&&... args){
    const char* comma = strchr(names + 1, ',');std::cerr.write(names, comma - names) << " : " << arg1<<" | ";__f(comma+1, args...);
}
template<typename T, typename U> static inline void amin(T &x, U y) 
{ 
    if (y < x) 
        x = y; 
}
template<typename T, typename U> static inline void amax(T &x, U y) 
{ 
    if (x < y) 
        x = y; 
}
 
ll max(ll a, ll b) { return (a > b)? a : b;}
int min(int a, int b) { return (a < b)? a : b;} 
const int N = (1<<21);
int poss[N];
int solve(){
 
    int n,k;
    cin>>n>>k;
 
    string s;
    cin>>s;
 
    int k2 = log2(n-k+1)+1;
    k2 = min(k,k2);
    int cnt[n+1];
    // memset(cnt,0,sizeof(cnt));
    cnt[0]=0;
    for(int i=0;i<n;i++){
        if(i)
            cnt[i] = cnt[i-1];
        cnt[i]+=(s[i]-'0');
    }
 
    int left = k - k2;
    for(int i=0;i<(1<<k2);i++)
        poss[i]=1;
 
    for(int i=0;i<=n-k;i++){
        int cur = 0;
        if(i+k-k2>=1)
            cur=cnt[i+k-k2-1];
        if(i)
            cur-=cnt[i-1];
        if(cur==k-k2 ){
            int x = 0;
            for(int j=k-k2;j<k;j++){
                x*=2;
                if(s[i+j]=='0') 
                    x++;
            }
            // trace(i,x);
            poss[x]=0;
        }
    }
    // trace(poss[0]);
            // trace(k2);
 
    for(int i=0;i<(1<<k2);i++){
        if(poss[i]){
            cout<<"YES"<<endl;
            string res="";
            while(i){
                if(i%2) res.pb('1');
                else res.pb('0');
                i/=2;
            }
            while(res.size()<k) res.pb('0');
            reverse(all(res));
 
            cout<<res<<endl;
            r0
        }
    }
 
    cout<<"NO"<<endl;
 
 
 
    return 0;
}
signed main(){
    asdf
    int t=1;
    cin>>t;
    while(t--){
        solve();
    }
    return 0;
}