This feels like a hack to me.  `@load_time` is internal state the spec shouldn't know about.  I'd much rather see something like this:

``` ruby
it "captures the load time so it can report it later" do
  formatter = instance_double(ProgressFormatter)
  reporter.register_listener formatter, :dump_summary
  reporter.start 3, 10

  expect(formatter).to receive(:dump_summary) do |notification|
    expect(notification.load_time).to eq(5)
  end

  reporter.finish
end
```