- This is controlled by specifying the 'mtstress' argument when running
`unit_test`.
- The goal is to detect if the operator/transformation fails in this
context.
- In this mode, the test will be executed 5'000 times in 50 threads
concurrently.
- Allocation & initialization of the operator/transformation is
performed once in the main thread, while the evaluation is executed in
the threads.
- This is consistent with the library's support for multithreading,
where initialization and loading of rules is expected to run once.
See issue #3215.
