Project architecture

[NickAb]

While this project is in early stage I thought it might be a good idea to discuss overall architecture and choose an approach for further development.

The project consists of two major components:

• The Driver, that runs on the host system and is responsible for managing emulators/devices, app under test deployment and staff like that.
• The automation Agent, that runs on the emulator/device and is responsible for actual automation of app under test.

I see three general approaches in building communication between these two components:

	Driver	⇄	Agent	Notes
1	Server (JSWP)	→	Server (RPC)	Currently used in Winium projects.
2	Server (JSWP)	↔	Client (WebSockets)	Agent has to connect to special endpoint on Driver. Driver uses two-way communications.
3	Server (JSWP Proxy)	→	Server (JSWP)	Similar to the first option, but agent implements full JSWP protocol. See facebook/WebDriverAgent

Here are some thoughts on each option.

1. Server (JSWP) → Server (RPC)

• Does not require implementing JSWP compatibility on both ends (Driver and Agent)
• Used in other Winium projects, appium-android-bootstrap
• Agent cannot be used without Driver directly from Selenium tests
• Agent is a server, i.e. requires a port to be bound to (ports are forwarded to host, complicating simultaneous run of multiple agents on multiple emulators on same host), etc.
• But we can use non-network RPC, for exapmle file based RPC if it is possible in cases of Agent (it is possible in Winium.StoreApps, where Agent is a part of the app under test)

2. Server (JSWP) ↔ Client (WebSockets)

• Does not require implementing JSWP compatibility on both ends (Driver and Agent)
• Does not require port to be bound to
• Two-way communications, which might be used for example for some extended functionality in inspector
• Agent cannot be used without Driver directly from Selenium tests

3. Server (JSWP Proxy) → Server (JSWP)

• Agent can be used directly without host Driver (except for deployment of agent, which can be done once (if it is stable enough))
• Kinda inevitable good separation of concerns: we have JSWP compatibly agent that can be used directly, we have emulator/devices management tool (similar to facebook/FBSimulatorControl), and simple JSWP proxy that overrides NewSession and a couple of other commands.
• Agent is a server, i.e. requires a port to be bound to (ports are forwarded to host, complicating simultaneous run of multiple agents on multiple emulators on same host), etc.
• Requires implementing JSWP compatibility on both sides