A testcase consists of a small chunk with a known result, and is sent to the client to test whether it really works or not. There are two types of testcases, one with a (known) result and one known to have no result. To make sure that a client/worker really works, for each jobtype there should be at least two testcases, one with a result, and one without a result.

a series of explicit actions and examinations that identifies the "what"

a command object