I was contacted via LinkedIn, responded several weeks later after getting a chance to research the company, and deciding it might be a good fit (I had initially not paid much attention to the message as I thought it was 'just another recruiter' and I had recently changed jobs).
There were some online assessments to take and a couple roles to choose from. I took both the tests and was asked to come in and interview/meet with the owners (one of whom ended up double booked). When I followed up a week or two later HR scheduled a time to come talk with the other partner.
The interview process was somewhat unusual. Mainly feeling me out. No specific technical questions or exercises. It was pretty clear by the direction of the conversation you might have a lot of trouble if you had lied about your experience, didn't care about software, or were in it for the wrong reasons/didn't really want to be working in the field. I would have been a deer in the headlights if I was fresh out of college.
I went back and met the owner who was double booked a couple weeks later. Similar experience. I could tell both the partners were heavily involved in day to day operations and had a large personal investment/commitment to the company. This was by far the easiest (for me) interview I've had, but it would definitely throw many (if not most) people off guard depending on personality.
Everything was very professional nonetheless, and I always got thoughtful responses to my follow ups. I didn't end up getting an offer, but suspect I could have given a little determination. My take was this would be a great place to work, with some of the 'start-up' fun but with the bar set pretty high regarding quality of work/expectations. Probably not for everyone but I'd recommend at least interviewing if you have the opportunity. Definitely not your average workplace.
