Video by Ayokoi, testing at Nishiya, junction of the Sotetsu Main Line and the connection to the JR Freight Line at Hazawa. Nishiya has a set of layover tracks for terminating services. Once through-running services begin in November, all services (not just locals) will stop at this station.
Sotetsu also recently had a press release detailing the service pattern for this new line. Trains will run from Ebina to Shinjuku (4 per hour at peak). A few will continue on in the direction of Omiya (details TBD)
https://www.sotetsu.co.jp/news_release/pdf/190716_01.pdf