Sure! Here is a test case generator for the given problem statement that calculates the area and circumference of a circle for a given radius \( r \).

```python
import random
import math

def tcgen():
    # Generate a random real number r in the range (0, 10000)
    r = random.uniform(1e-5, 9999.99999)
    
    # Calculate the area and circumference
    area = math.pi * r * r
    circumference = 2 * math.pi * r
    
    # Return the generated test case and the expected output
    return r, f"{area:.6f} {circumference:.6f}"

# Example of generating a test case
r, output = tcgen()
print(f"Generated Test Case: r = {r}")
print(f"Expected Output: {output}")
```

### Explanation:

1. **Generating \( r \)**: 
    - We use `random.uniform(1e-5, 9999.99999)` to generate a random floating-point number \( r \) in the range (0, 10000). This ensures that \( r \) is always greater than 0 and less than 10000.
    - The lower bound `1e-5` is used to avoid generating an \( r \) that is too close to 0, which might make the area and circumference calculations trivial.

2. **Calculating the Area and Circumference**:
    - The area of the circle is calculated using the formula \( \text{area} = \pi r^2 \).
    - The circumference of the circle is calculated using the formula \( \text{circumference} = 2 \pi r \).

3. **Formatting the Output**:
    - We format the area and circumference to six decimal places using the format string `"{:.6f}"`, ensuring the output meets the precision requirement.

4. **Returning the Test Case and Expected Output**:
    - The function returns the generated radius \( r \) and the formatted expected output as a string.

5. **Example Usage**:
    - The example usage shows how to generate a test case and print the generated radius and expected output.

You can use this function to generate multiple test cases for your problem.