A function to change the value of Build.VERSION

TestHelpers.kt

object TestHelpers {
    // Usage: TestHelpers.setSdkVersion(Build.VERSION_CODES.P)
    fun setSdkVersion(version: Int) {
        val field = Build.VERSION::class.java.getField("SDK_INT")
        field.isAccessible = true

        val modifiersField = Field::class.java.getDeclaredField("modifiers")
        modifiersField.isAccessible = true
        modifiersField.setInt(field, field.modifiers and Modifier.FINAL.inv())

        field.set(null, version)
    }
}