Sure! Here's the test case generator for the problem statement you provided:

```python
import random

def tcgen():
    # Generate N within the range [1, 100]
    N = random.randint(1, 100)
    
    # Generate i within the range [1, N]
    i = random.randint(1, N)
    
    return N, i

# Example usage
for _ in range(5):  # Generating 5 test cases
    N, i = tcgen()
    print(f"Generated test case: N = {N}, i = {i}")
```

Explanation of the test case generator:
1. **Generate `N`**: We randomly generate an integer `N` within the range [1, 100] as per the given constraints.
2. **Generate `i`**: We then randomly generate an integer `i` within the range [1, N], ensuring it is a valid car position in the train.
3. **Return `N` and `i`**: The function returns these values as a tuple, which represents a single test case for the problem.

You can use the `tcgen` function to generate multiple test cases and print them out or use them in your testing framework.