I Already Have Platform-specific Tests For My App, What Should I Do To Migrate To Appium?

Unfortunately, there is no magic formula to translate your tests into Selenium tests. If you developed a test framework on different layers and observed good programming principles, you should be able to act on some components in your tests in order to migrate your suites to Appium.

Your current tests are going to be easy to migrate if they are already using an automation framework or something close to a command-based interaction. Truth be told, you will probably need to write your tests from the beginning.