#include <bits/stdc++.h>
using namespace std;
#define optimize() ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
#define all(v) (v).begin(),(v).end();
#define rall(v) (v).rbegin(),(v).rend();
#define ll long long
#define endl '\n'
#define gap " "
#define bug(a) cerr<<#a<<":"<<endl;
int main()
{
    ll n;
    cin>>n;
    while(n--)
    {
        ll n1;
        cin>>n1;
        string s,s1;
        cin>>s>>s1;
        ll i,j;
        string s3;
        s3+=min(s[0], s1[0]);
        for(ll i=1;i<n1;i++)
        {
            char check=min(s[i],s1[i]);
            char check1=max(s[i],s1[i]);
            if(check>=s3[i-1]) s3.push_back(check);
            else s3.push_back(check1);
        }
        //cout<<s3<<endl;
        string s4=s3;
        sort(s4.begin(),s4.end());
        if(s3==s4)cout<<"Yes"<<endl;
        else cout<<"No"<<endl;
    }
    
}