dirname() is a slow function compared with __DIR__ and using
'/../'. Moodle has a large number of legacy files that are included
each time a page loads and is not able to use an autoloader as it is
functional code. This allows those required includes to perform as
best as possible in this situation.
This parallels question_attempt->minfraction, which allows the
fractional mark to go below zere.
This is needed to allow the certainty-base marking behaviours to work
better.
1. Autosave works in some ways just like a normal save. We ultimately
call $behaviour->process_save() to do the work, and create a new step to
hold the data.
2. However, we come in through a completely different route through the
API, starting with separate auto-save methods. This keeps the auto-save
changes mostly separate, and so reduced the chance of breaking existing
working code.
3. When the time comes to store the auto-save step in the database, we
save it using a negative sequence number.
This is a clever trick that not only distinguises these steps, but also
avoids unique key errors when an auto-save and a real action happen
simultaneously. (There are unit tests for these tricky edge cases.)
4. When we load the data back from the database, most of the time the
auto-save steps are loaded back as if they were a real save, and so the
auto-saved data is used when the question is then rendered.
5. However, before we process another action, we remove the auto-saved
step, so it does not appear in the final history.
1. Split the question_attempt tests into one class per file.
2. Imporve the API to give tests more control, and to test more of the
important code. Some of this is not used here, but it is about to be.
