#include<bits/stdc++.h>
using namespace std;
#define int long long
void solve()
{
    int n;cin>>n;
    string s1,s2;cin>>s1>>s2;
    char c = 'a';
    s1[0] = min(s1[0],s2[0]);
    c=s1[0];
    for(int i=1;i<s1.size();i++)
    {
        char q;
        if(s1[i]<=s2[i])q=s1[i];
        else q = s2[i];
        if(q>=c)
        {
            s1[i] = q;
        }
        c = s1[i];
    }
    int flag=1;
    for(int i=0;i<n-1;i++)
    {
        if(s1[i+1]<s1[i])
        {
            flag=0;
            break;
        }
    }
    if(flag)cout<<"Yes"<<endl;
    else cout<<"No"<<endl;
}
int32_t main()
{
    int t=1;
    cin>>t;
    for(int i=1;i<=t;i++)
    {
        //cout<<"Case : "<<i;
        solve();
    }

}