#include <bits/stdc++.h>
using namespace std ;
#define int long long
#define opt() ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0);
const int N = 2e5+10 ;
const int mod= 1e9+7 ;
#define pb push_back
#define mp make_pair

int32_t main()
{
    opt();
    int tt=1;
    cin>>tt;
    for(int tc=1; tc<=tt; tc++)
    {
        int n ;
        cin>>n ;
        string s1,s2 ;
        cin>>s1 >>s2 ;
        string  ans ;
        if(s1[0]>s2[0])ans.pb(s2[0]);
        else ans.pb(s1[0]);
        bool f=false;

        for(int i=1; i<n-1; i++)
        {

            bool ok=false;
            char tm,tmp1;
            if(s1[i]>s2[i])tm=s2[i],tmp1=s1[i];
            else tm=s1[i],tmp1=s2[i];
            if(tm>=ans.back() ||tm>=ans.back() )
            {

                if(tm<=s1[i+1] || tm<=s2[i+1])
                {

                    ok=true;
                    ans.pb(tm);
                }
            }
            if(!ok)
            {
                if(tmp1>=ans.back() ||tmp1>=ans.back() )
                {

                    if(tmp1<=s1[i+1] || tmp1<=s2[i+1])
                    {

                        ok=true;
                        ans.pb(tmp1);
                    }
                }

            }
            if(!ok)
            {
                f=true;
                break;
            }
        }
        //cout << ans <<"\n" ;
        if(s1[n-1]<=s2[n-1])ans.pb(s2[n-1]);
        else ans.pb(s1[n-1]);

        if (!(is_sorted (ans.begin () ,ans.end ())) )f=true;
        cout<<(f?"No":"Yes")<<endl;

    }
}