custom matcher which asserts outside of expect (something like "expect to receive")

[Kris Leech]

I've been trying for a while to write a custom matcher for my gem Wisper, which provides pub/sub for Ruby objects.

Wisper uses `public_send` to publish an event to subscribed listeners.

At the moment without a custom matcher I can subscribe a double to a publisher and assert the method (i.e. event) is received.

publisher = Class.new do
  include Wisper::Publisher

  def execute
    broadcast(:successful) # this will do `public_send(:successful)` on every subscriber
  end
end.new

subscriber = double

publisher.subscribe(subscriber)

expect(subscriber).to receive(:successful)

publisher.execute

BUT... what I really want to do is this:

publisher = ...

expect(publisher).to publisher(:successful)

publisher.execute

I've tried a few things, but I can't seem to get it to work unless `expect` is given a block in which the publisher's `execute` method is called, i.e.

expect { publisher.execute }.to broadcast(:successful)

I'd like something more akin to `receive` where the actual assertion does not have to happen within the `expect`, but can happen later.

https://github.com/krisleech/wisper/blob/rspec-matcher/lib/wisper/rspec/matchers.rb

https://github.com/krisleech/wisper/blob/rspec-matcher/spec/lib/wisper/rspec/matchers_spec.rb <- this shows the passing and failing spec (prefer syntax)

Any pointers would be gratefully received (no pun intended). Also I'm unsure of the difference between a matcher and expectation, are they the same or different?

- Kris.