No one has mentioned Upcase yet! It's a learning platform by Thoughtbot that has just recently gone free.
They have a Weekly Iteration which is like 20 mins bite size videos that I watch every now and then.
I also do their Trails (which are like longer, series of course), some of them being Test Driven, Foundations of Testing etc during weekends!
The testing bits really helped me a bunch :)
I don't think they're highly actively maintained anymore but it's still a great library of resources nonetheless!
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