I applied online, and was contacted the next day over e-mail with next steps to follow. I had an informal phone screen with a Tenable representative from Talent Acquisition, which went well. From there I was given a simple code test to complete and return. I asked some questions about the test to refine my answer, and then sent my answers along.
I sent my code test answer in mid-December, and heard back in early January that my work looked good and that we were proceeding to (virtual) interviews. The delay was understandable due to the holiday season, so I accepted the interview invite. I had one interview with a fellow engineer, and from there I was offered a second interview with a software engineering manager. That interview also went well. Within a week of that interview, I was given an offer and accepted.
Both interviews were pretty informal, and the questions were not super-focused on Tenable's code test, but more about general code philosophy, as well as past experience (personal and professional).