From e-Learning Documentation
There are two online testing tools in Sakai, Assessments and Tests & Quizzes. You may choose whichever of these tools best meets your needs. In general, Tests & Quizzes offers more function than Assessments, but many people find the Assessments tool more intuitive and easier to use.
The two tools are very different in their approach to online testing.
Assessments REQUIRES the use of Question Pools and those Question Pools MUST be structured in a specific way. Question Pools must contain questions of the same point value and difficulty level. This is a good practice and a helpful way to set up your Question Pools, resulting in a very nicely organized collection of Question Pools. Assessments also has an easy process for assigning an assessment to special needs students that need added time, but there is no option to assign an assessment to a group.
Assessments also offers the option to require students to acknowledge the Honor Pledge before they can submit the assessment. Certain question types, Multiple Choice, True/False, and Essay, can be imported into Assessment from Respondus. Question Pools can be imported from Tests & Quizzes into Assessments.
Probably the biggest limitation of Assessments is that once an assessment has been accessed, even by a Test Drive, that Assessment cannot be edited or deleted. It can only be archived.
Tests & Quizzes offers Question Pools, but does not require their use. You may enter questions directly into an assessment without those questions being assigned to a Question Pool. You can have questions of varied difficulty levels and point values in one Question Pool. You can create Sub-Pools within Question Pools to further aid organization. Question Pools in Tests & Quizzes are associated with the creator's Username, not the course in which the pools were created. So if you are instructor for ABC1234 and CBA4321 and you create five Question Pools in ABC1234, you will also see those five pools when you go to your CBA4321 course. This is helpful in that you always have access to your Question Pools, but it requires you to pay attention to naming conventions. You would not want to name a Question Pool "Exam 1."
Tests & Quizzes offers the added security of limiting an assessment to a specific IP address, or group of IP addresses. You have the ability to show students the statistics on an assessment and individual questions within the assessment. Questions can only be entered manually, or by cutting and pasting a properly formatted text document. An assessment in Tests & Quizzes can be assigned to a group. You can edit many aspects of a published assessment, including the ability to edit a question and regrade the assessment.