Sure! The problem statement for "Circular Sugoroku" is clear, and to generate test cases, we need to ensure that we cover various scenarios within the given constraints. Here's the Python code for generating test cases for this problem:

```python
import random

def tcgen():
    # Number of squares, N (1 ≤ N ≤ 100000)
    N = random.randint(1, 100000)
    
    # List of integers a1, a2, ..., aN where each ai (1 ≤ ai ≤ 10^9)
    A = [random.randint(1, 10**9) for _ in range(N)]
    
    return N, A

# Example of generating one test case
if __name__ == "__main__":
    N, A = tcgen()
    print(N)
    print(" ".join(map(str, A)))
```

### Explanation

1. **N**: This is the number of squares in the sugoroku board. The value is randomly generated between 1 and 100,000 inclusive.
2. **A**: This is the list of integers representing the number of squares to move clockwise from each square. Each value in the list is randomly generated between 1 and 1,000,000,000 inclusive.

### Usage

- Running the script will generate a random test case within the constraints.
- The printed output will be in the format required by the problem statement, suitable for testing purposes.

This generator ensures that the test cases are diverse and cover the edge cases within the specified limits, which is crucial for thoroughly testing the implementation of the solution to the problem.