#include <bits/stdc++.h>
#define ll long long
#define F first
#define S second
#define endl '\n'
#define Endl '\n'

using namespace std;

const int N = 2e5 + 5;
int tc, n, m, a[N];

int main() {
    ios_base::sync_with_stdio(0);
    cin.tie(0); // cout.tie(0);
    cin >> tc;
    while (tc--) {
        string x, y;
        cin >> n >> x >> y;
        bool hasAns = true;
        char lastChar = 'a';
        for (int i = 0; i < n; i++) {
            int minChar = min(x[i], y[i]);
            int maxChar = max(x[i], y[i]);
            if (minChar >= lastChar) {
                lastChar = minChar;
            } else if (maxChar >= lastChar) {
                lastChar = maxChar;
            } else {
                hasAns = false;
                break;
            }
        }
        cout << (hasAns ? "Yes" : "No") << endl;
    }

    return 0;
}