Sure! Here is a test case generator for the given problem statement "A Light Road":

```python
import random

def generate_grid(N, M, A):
    grid = [['.'] * M for _ in range(N)]

    # Place obstacles randomly
    num_obstacles = random.randint(0, (N * M) // 3)
    for _ in range(num_obstacles):
        x, y = random.randint(0, N - 1), random.randint(0, M - 1)
        grid[x][y] = '#'
    
    # Place the laser generator 'S'
    while True:
        sx, sy = random.randint(0, N - 2), random.randint(0, M - 1)
        if grid[sx][sy] == '.':
            grid[sx][sy] = 'S'
            break
    
    # Place the evil creature 'G'
    while True:
        gx, gy = random.randint(1, N - 1), random.randint(0, M - 1)
        if grid[gx][gy] == '.':
            grid[gx][gy] = 'G'
            break
    
    return grid

def tcgen():
    N = random.randint(2, 100)
    M = random.randint(2, 100)
    A = random.randint(0, 10)
    
    grid = generate_grid(N, M, A)

    # Convert grid to the required format
    grid_input = '\n'.join([''.join(row) for row in grid])
    
    return f"{N} {M} {A}\n{grid_input}"

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

This script generates random test cases for the problem "A Light Road". It ensures that there is exactly one laser generator (`'S'`) and one evil creature (`'G'`) on the grid, and places a random number of obstacles (`'#'`). The number of mirrors (type `P` and type `Q`) is also chosen randomly within the constraint \(0 \leq A \leq 10\). 

Please note that the script does not ensure that the generated test case always has a valid path for the laser to kill the creature. It only ensures the grid is generated according to the constraints given in the problem statement.