After Mumbai CR Went under AC traction, as a part of 'Tests' were performed on all four lines. Testing started at about 5:48 in the morning and continued in a very quick span of time!
As such, in this video you can see an EMU under AC traction skipping TNA from Pf4, and simultaneously, GOC WDP4D 40014 entering Thane Stn with 12051 Madgoan Janshatabdi Express in tow for a scheduled halt.