Rails CollectionProxy #length vs #count

When testing a controller, it's not unreasonable to right a test something like this:

expect(post_to_endpoint).to change { some.objects.length }.from(0).to(1)

Because of the details of CollectionProxy, this will not work as expected. Instead, you need to write:

expect(post_to_endpoint).to change { some.objects.count }.from(0).to(1)

The length method will evaluate to the same value, while the count method will reflect changes to the underlying data since the last call.