Certainly! Below is a test case generator for the "Sum of Decimal Digits" problem statement.

```python
import random

def tcgen():
    datasets = []
    num_datasets = random.randint(1, 100)

    for _ in range(num_datasets):
        a = random.randint(1, 1000)
        b = random.randint(1, 10000)
        n = random.randint(1, 100)
        datasets.append((a, b, n))
    
    return datasets

# Example usage:
random.seed(0)  # Optional: for reproducibility
test_datasets = tcgen()

for dataset in test_datasets:
    print(f"{dataset[0]} {dataset[1]} {dataset[2]}")
```

This generator creates a random number of datasets (between 1 and 100). For each dataset, it generates three integers \(a\), \(b\), and \(n\) within the specified ranges. Each dataset is stored as a tuple in the list `datasets`. Finally, the generator returns the list of datasets.

You can use the example usage provided to print the generated test cases. Note that the `random.seed(0)` line is optional and can be used to ensure reproducibility of the generated test cases for debugging or testing purposes.