Sure, I can write a test case generator for the given problem statement. Here’s how you can generate test cases for this problem:

```python
import random

def tcgen():
    # Generate two equal numbers
    common_value = random.randint(-100, 100)
    
    # Generate a different number
    different_value = common_value
    while different_value == common_value:
        different_value = random.randint(-100, 100)
    
    # Place the different value in a random position among the three
    positions = [common_value, common_value, different_value]
    random.shuffle(positions)
    
    A, B, C = positions
    return A, B, C

# Example usage:
for _ in range(5):
    print(tcgen())
```

Here's a breakdown of the test case generator:
1. **Generate two equal numbers:** `common_value` is randomly chosen within the range -100 to 100.
2. **Generate a different number:** `different_value` is chosen such that it is different from `common_value`.
3. **Place the different value randomly:** The different number is shuffled into one of the three positions (A, B, C).

This generator strictly follows the constraints and ensures that two out of the three numbers are the same, and one is different.