Some tests are highly focused, and only look for a single issue. For example, the Spelling test simply detects words with unrecognized spellings.
Other tests may encompass a wide range of checks, such as Metadata, which performs many checks on page titles, descriptions and images. These checks are grouped together under a single test to make them easier to use and work with.
You can think of tests as a kind of ‘app within Insites’. Tests can be enabled and disabled as needed.