Generating test cases for a problem like "Quadruplet Primes" involves simulating multiple datasets with varying values of \( n \), including edge cases and random cases within the specified range. The generator will need to handle multiple datasets and ensure that the end of input is indicated correctly.

Here is a test case generator for the "Quadruplet Primes" problem:

```python
import random

def is_prime(num):
    """ Helper function to check if a number is prime. """
    if num <= 1:
        return False
    if num <= 3:
        return True
    if num % 2 == 0 or num % 3 == 0:
        return False
    i = 5
    while i * i <= num:
        if num % i == 0 or num % (i + 2) == 0:
            return False
        i += 6
    return True

def find_quadruplet_primes(n):
    """ Find all quadruplet primes up to n. Returns a list of sizes of quadruplet primes. """
    quadruplet_primes = []
    for a in range(2, n - 7):
        if is_prime(a) and is_prime(a + 2) and is_prime(a + 6) and is_prime(a + 8):
            quadruplet_primes.append(a + 8)
    return quadruplet_primes

def tcgen():
    """ Test case generator for the Quadruplet Primes problem. """
    num_datasets = random.randint(1, 2000)
    test_cases = []
    
    for _ in range(num_datasets):
        n = random.randint(13, 10000000)
        test_cases.append(n)
    
    # Ensure we include edge cases
    test_cases += [13, 10000000, 0]
    
    return test_cases

# Generate test cases
test_cases = tcgen()

# Print the test cases in the needed format
for case in test_cases:
    print(case)
```

Explanation:
1. **Prime Checking Function**: `is_prime` is a helper function used to determine if a number is prime.
2. **Quadruplet Primes Finder**: `find_quadruplet_primes` function is used to find all quadruplet primes up to a given number \( n \).
3. **Test Case Generation (`tcgen`)**:
   - Generates a random number of datasets (between 1 and 2000).
   - For each dataset, a random number \( n \) is selected within the given range (13 to 10,000,000).
   - Edge cases are explicitly added (like the smallest and largest possible \( n \), and the termination input `0`).

**Note**: For competitive programming problems, it's crucial to include edge cases to ensure the robustness of the solution. This generator focuses on producing varied and comprehensive test cases, including edge cases and random valid inputs.