rrule_test requires returned composite objects to be collectable

`rrule_test` use `collect` to get the field of composite objects, but it is not always possible, as for e.g. `qr`

```
F = qr(randn(5, 5))
Q, R = F  # Valid since F is iterable
collect(F)  # Errors since length is not defined on LinearAlgebra.QRCompactWY
```

Using `[y...]` instead of `collect(y)` should do the trick.