Add mobile device testing to SeleniumBase

[mdmintz]

Add mobile device testing to SeleniumBase

Use --mobile to quickly run your tests using Chrome's mobile device emulator with default values for device metrics (CSS Width, CSS Height, Pixel-Ratio) and a default value set for the user agent. To configure the mobile device metrics, use --metrics="CSS_Width,CSS_Height,Pixel_Ratio" to set those values. You'll also be able to set the user agent with --agent="USER-AGENT-STRING" (a default user agent will be used if not specified). To find real values for device metrics, see this GitHub Gist. For a list of available user agent strings, check out this page.

# Run tests using Chrome's mobile device emulator (default settings)
pytest test_swag_labs.py --mobile

# Run mobile tests specifying CSS Width, CSS Height, and Pixel-Ratio
pytest test_swag_labs.py --mobile --metrics="411,731,3"

# Run mobile tests specifying the user agent
pytest test_swag_labs.py --mobile --agent="Mozilla/5.0 (Linux; Android 9; Pixel 3 XL)"