#include<bits/stdc++.h>
using namespace std;

#define int long long
#define endl "\n"
#define pii pair<int, int>
#define int long long


void solve() {
    int n; cin>>n;
    string s, t; cin>>s>>t;
    s[0] = min(s[0], t[0]);
    for(int i = 1; i < n; i++) {
        if(s[i] < s[i - 1]) {
            if(t[i] < s[i - 1]) {
                cout<<"No"<<endl;
                return;
            }
            s[i] = t[i];
        } else {
            if(t[i] >= s[i - 1])
                s[i] = min(s[i], t[i]);
        }
    }

    cout<<"Yes"<<endl;
}

 
signed main() {
	ios_base::sync_with_stdio(false);
	cin.tie(NULL);

	int t = 1; cin>>t;
	for(int i = 1; i <= t; i++) {
		// cerr<<"Case "<<i<<": \n";
		solve();
	}
}