Appium Architecture 

This video explains how Appium works for mobile automation testing.
Appium Webdriver, client server architecture with all external drivers are explained.
Appium is an open-source automation tool for testing mobile applications on various platforms. Internally, Appium works by interacting with the mobile application just like a real user would. Here's a simplified overview of its internal workings:
1. *Server-Client Architecture:* Appium follows a client-server architecture. The Appium server acts as a bridge between your test script (written in a programming language like Java, Python, etc.) and the mobile device or emulator.
2. *Client Libraries:* Appium provides client libraries in various programming languages, enabling you to write your test scripts in the language of your choice. These scripts send commands to the Appium server.
3. *WebDriver Protocol:* Appium implements the WebDriver protocol, which is a standardized way of interacting with web and mobile applications. This protocol defines a set of commands and responses that allow automation scripts to control the behavior of applications.
4. *Platform-Specific Drivers:* Appium uses platform-specific automation frameworks to interact with the mobile device. For iOS, it uses XCUITest, and for Android, it uses UIAutomator or UIAutomator2. These frameworks provide the low-level interactions required for automation.
5. *JSON Wire Protocol:* The communication between the client and the server is done using the JSON Wire Protocol, a RESTful API that sends JSON payloads with commands and receives JSON responses.
6. *Automation Scripts Execution:* Your automation scripts include commands to interact with the elements of the mobile application, such as tapping buttons, entering text, or swiping gestures. These commands are translated by the Appium server into actions that the mobile automation frameworks can understand.
7. *Instrumentation and App Installation:* Appium installs a testing automation framework (like Appium's own app for Android or an XCUITest bundle for iOS) on the device or emulator to enable communication and interaction with the application under test.
In summary, Appium uses a combination of client-server communication, platform-specific automation frameworks, and the WebDriver protocol to facilitate the automation of mobile applications across different platforms.
After this video, you should get answer to your question: What is appium in software testing and how does it work for iOS devices.