I have the follow situation

Scenario

Part 1. An app working with Build Variants: debug, beta and release as follow

buildTypes {
    debug {
        versionNameSuffix '-DEBUG'
        applicationIdSuffix '.debug'
        buildConfigField "String", "SERVER_URL", '"url local test"'
        debuggable true
        signingConfig signingConfigs.config
    }
    beta {
        versionNameSuffix '-BETA'
        buildConfigField "String", "SERVER_URL", '"url homologation"'
        signingConfig signingConfigs.config
    }
    release {
        buildConfigField "String", "SERVER_URL", '"url production"'
        minifyEnabled false
        proguardFiles getDefaultProguardFile('proguard-android.txt'), 'proguard-rules.pro'
        signingConfig signingConfigs.config
    }
}

And a call to use String SERVER_URL pointing to current url by buildType selected. Look this

String URL = BuildConfig.SERVER_URL

Part 2. The switch between Build Variants by Android Studio, as follow image

It's working absolutelly fine for me

Issue

Part 1. I have the app on Google Play production generated as signed apk from release variant

Part 2. I need put the app on Google Play beta test generating as signed apk from BETA variant, e.g, pointing to url homologation

Part 3. When the product owner finish the tests from beta test, I go need promote the same app to production by Google Play Console

Question

The core question: When I go promote the app from beta to production, it one will point automatically to url production by release variant or I will need generate another apk as signed apk from release variant?

Why? The main motivation is beacause I can't test this promotion without safe assurance that it will work fine, and no less important, this would save my time and my own chef would can do it

Alert! If it is wrong job, what the best pratice to do it?

If I understand your question it is this:

• with your current setup, you have some configuration compiled into the APK, including a server URL
• you want to test with one server in beta, and a different one in release
• but this means you can't promote your beta APK to release, because the URL would be different. But if you re-compile, you can't be sure the APK remains unchanged from the one you tested.

You are right, this is a real problem. There are two common solutions:

• Option 1: don't compile your server strings into your APK. Instead, use a service like Firebase remote config to dynamically change the server and other settings for your beta. That way the APK doesn't need to change
• Option 2: When you build your beta build, tag your branch in your version control system. Then when you want to promote to prod, build a new APK, but make sure you are using the tagged branch from the version control system.

Personally I think I would recommend option 1, but I know different large professional android developers use both options.