How can I create an Xiaomi emulator for Android Studio? Or any other way to test app on Xiaomi emulators?

You can try genymotion but currently it has Xiaomi Redmi Note 7

1. You can use some online device provider services like : browserstack

2. I never tried it but check out : Run custom ROM on Android Emulator

3. You can always borrow / buy an actual device.

1. Menu Tools → AVG Manager

2. Click on "Create Virtual Device"

3. Select "Phone" in the left

4. Click "New Hardware Profile" button below

5. Use the following information in the next screen:

   Device Name: Redmi Note 5
   Device Type: Phone/ Tablet
   Screen Size: 5.99 Inch
   Resolution: 1080 x 2160 px
   Memory: 4 GB
   Input: <Leave these un-selected>
   Rest of the fields: keep as is.

   Save it and select it.

6. Click "Next" below to go to the next page "Select a system image". Select the Release you want. E.g., Oreo [Target: Android 8.1]. Click "Next" to "Verify Configuration". Name the AVD - something like "Redmi Note 5 Oreo"

Finish.

Enjoy!!

Here are the steps with Android Studio: