Testbanks: zyBooks provides multiple-choice testbank questions for several zyBooks (Computing Technology for All, Python, Java, C++, Operating Systems, and Discrete Math), and continues to add testbanks for others. The testbanks are designed to be printed for a paper exam (we output to MS Word), or they can be outputted to the "QTI" format for uploading into a learning management system (LMS) like Canvas, Blackboard, and Brightspace. See this article for info on creating tests using our testbanks.
zyBooks itself does not have features for administering tests online. Instead, instructors can upload our test questions into their LMS, and then use the exam administering capabilities of the LMS. There are also other companies that specialize in online exams, like Respondus.
zyLabs: zyBooks also provides the zyLab program auto-grader, which although we explicitly tell instructors was not designed for exams, nevertheless is used by over 100 schools (we know of) for exams. As long as instructors are comfortable with what they are doing, we're fine with that.
Focus on exams: With the above said, we'll note that we get a lot of requests for exam capabilities, and have prioritized providing more direct support for exams -- both for multiple choice and auto-graded programs -- in 2020.
COVID-19 and online exams -- The COVID-19 situation in 2020 has accelerated online exam needs, as more schools are teaching classes online to avoid students coming together in a room. Of course, this brings up yet a distinct online exam situation of at-home online exams (vs. online exams taken in a controlled lab setting, as is the common case). Preventing "inappropriate help" for at-home exams is especially hard. Several companies specialize in at-home proctored exams, like Examity or ProctorU, though it's possible they might be overwhelmed due to the surge in demand due to COVID-19. The online exam situation will likely evolve and progress rapidly in 2020.