Wanna try out Stardew Valley's multiplayer test? So EASY!
Here are the instructions:
Log into your Steam account
In your Games Library, right click on Stardew Valley
Select Properties → Betas (see: https://imgur.com/a/H1gH4)
Enter the Beta access code “jumpingjunimos” and press Check Code
After this, select the beta branch option on the Beta selection drop down list above
And boom! You're good to go! ENJOY!!