How do i construct all the Corner/Sample Cases for CHFING Problem?

Can anyone provide a corner/sample test case for the CHFING(Chef and Ingredient) problem from codechef? I am getting wrong answer when i submit but i am getting the answer correctly for all the test cases that i can come up with.

I have tried finding the pattern with with three conditions

1) N>K

2) N<=K

3) K=1

Is there anything that i am missing?

This is my Code

#include <bits/stdc++.h>

#define FOR(i, a, b) for (int i = a; i < b; ++i)
#define ROF(i, a, b) for (int i = a; i >= b; --i)
#define vi vector<int>

using namespace std;

int main()
{

    int T;
    long long int N, K, MOD = 10e9 + 7;
    cin >> T;
    while (T--)
    {
        cin >> N >> K;
        if (N < K)
        {
            cout << (K + abs(K - 1 - N)) % MOD << endl;
        }
        else if (N >= K)
        {
            cout << (K - 1) % MOD << endl;
        }
        else
        {
            cout << 0 << endl;
        }
    }
    return 0;
}