CodeRunner Documentation (V3.2.1)
Templates are the key to understanding how a submission is tested. Every question has a template, either imported from the question type or explicitly customised, which defines how the executable program is constructed from the student's answer, the test code and other custom code within the template itself.
A question's template can be either a per-test template or a combinator template. The first one is the simpler; it is applied once for every test in the question to yield an executable program which is sent to the sandbox. Each such execution defines one row of the result table. Combinator templates, as the name implies, are able to combine multiple test cases into a single execution, provided there is no standard input for any of the test cases. We will discuss the easier per-test template first.