#include<iostream>

#include<cstring>

#include<cstdio>

#include<vector>

#include<queue>

using namespace std;

const int maxn = ;

const int INF = 0x3f3f3f3f;

struct Edge {

    int v, w;

    Edge(int v, int w) :v(v), w(w) {}

    Edge() {}

};

int n, m,k;

vector<Edge> egs;

vector<int> G[maxn];

void addEdge(int u, int v, int w) {

    G[u].push_back(egs.size());

    egs.push_back(Edge(v,w));

}

bool inq[maxn];

int cnt[maxn];

int d[maxn];

bool spfa() {

    memset(inq, , sizeof(inq));

    memset(cnt, , sizeof(cnt));

    for (int i = ; i <= n + m; i++) d[i] = INF;

    queue<int> Q;

    d[] = ; inq[] = true; Q.push();

    while (!Q.empty()) {

        int u = Q.front(); Q.pop();

        inq[u] = false;

        for (int i = ; i < G[u].size(); i++) {

            Edge& e = egs[G[u][i]];

            if (d[e.v] > d[u] + e.w) {

                d[e.v] = d[u] + e.w;

                if (!inq[e.v]) {

                    Q.push(e.v);

                    inq[e.v] = true;

                    if (++cnt[e.v] > n+m+) {

                        return false;

                    }

                }

            }

        }

    }

    return true;

}

void init() {

    for (int i = ; i <= n + m; i++) G[i].clear();

    egs.clear();

}

int main() {

    int tc;

    scanf("%d", &tc);

    while (tc--) {

        scanf("%d%d%d", &n, &m, &k);

        init();

        for (int i = ; i < k; i++) {

            int u, v, w;

            scanf("%d%d%d", &u, &v, &w);

            addEdge(u, v+n, w);

            addEdge(v+n, u, -w);

        }

        for (int i = ; i <= n + m; i++) {

            addEdge(, i, );

        }

        if (spfa()) {

            puts("Yes");

        }

        else {

            puts("No");

        }

    }

    return ;

}

/*

2

2 2 4

1 1 0

1 2 0

2 1 2

2 2 2

2 2 4

1 1 0

1 2 0

2 1 2

2 2 1

*/