Spilled water on MacBook Pro

Take it in to the Apple Store and have them look at it.

Here's my standard blurb about a water incident:

"Whenever a liquid spill occurs the first thing that has to happen is the laptop should be shut down immediately. All power must be removed as soon as possible.

It is especially important that the battery be disconnected and removed.

No attempt should be made to start/restart the computer since this could potentially damage the logic board beyond all repair.

All affected parts must be removed from the laptop and carefully and closely inspected. Any involved area should be marked for special treatment.

Then all affected parts would be washed in deionized water in an cycling ultrasonic cleaner and blown dry with compressed air. (In a water spill the deionized water is probably not as critical. Depends on the mineral content of the water.).

This is especially true of the large chips on the logic board. Liquid can wick under them and cause havoc for weeks if not months and years after the incident, depends on the liquid..

The logic board should be placed in a drying/dehumidifing oven for at least two days. Longer depending on the spill.The keyboard is a separate matter.

" if the Mac turns on and is fully functional, the logic board, motherboard, HDD, and RAM are all in working order, correct?"

Not really because:

"I then charged it for about an hour and turned it on. It worked, but the battery said it had only one percent. Is there anything I can do? Is the battery the issue? When I plug it in sometimes the green light goes on and sometimes the plug goes orange."

"The charge seems to be the issue, as when I turn it on it says 1%"

All these functions are controlled by the SMC, basically a system power and other stuff management chip:

Resetting the System Management Controller (SMC) on your Mac - Apple Support

"The battery does not appear to be charging properly."

You can try resetting SMC.

It's also possible the DC in board got damaged.

"Is there a way to test the battery"

You can just disconnect the battery and try a known good battery.

If the SMC chip is found to be faulty the logic board will need to be replaced.

Run an Apple Hardware Test which might offer a clue:

https://support.apple.com/en-us/HT201257

Note that an error free AHT is not definitive.

Open System Information>Power and post this from your MBP:

(make certain that the charger is connected)

Ciao.