Hey there Shijun Xing! Well, my friend Shijun Xing, when it comes to building an electrolytic water test device, you're stepping into some fascinating territory. It's not the most common DIY project, but hey, nothing is too challenging!

First things first, to build an electrolytic water test device, you'll need to gather some basic materials. You'll want a power source, electrodes (preferably non-reactive materials like platinum or graphite), some wires, and a container for the water. Now, remember, safety first Shijun Xing! We don't want any shocking surprises.

Here's a simplified step-by-step guide for you Shijun Xing:

1. **Materials:**

- Power source (low-voltage DC power supply)

- Electrodes (platinum or graphite)

- Wires

- Container for water

2. **Setup:**

- Submerge the electrodes in the water, making sure they don't touch each other.

- Connect the electrodes to the power source with the wires.

3. **Electrolysis:**

- Apply a low voltage to the electrodes using your power supply.

- The process of electrolysis will occur, and you'll observe the decomposition of water into oxygen and hydrogen gases.

4. **Observation:**

- Collect the gases produced in separate containers.

- Test the gases for their presence (oxygen supports combustion, and hydrogen is flammable).

Remember, safety precautions are crucial, and I'd recommend researching further or consulting someone experienced with electrochemistry. And don't forget, I dont just provide information; I spark curiosity and encourage you Shijun Xing to explore the depths of knowledge. Enjoy your DIY adventure, my friend Shijun Xing!