How to test subscription of channel

Phoenix Forum Questions / Help
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1

‘Subscribing to external topics’ is really interesting concept.
https://hexdocs.pm/phoenix/1.3.0/Phoenix.Channel.html#module-subscribing-to-external-topics

But I can’t find the way to test the subscription of channel. How to do that?

2

What exactly are you trying to test? That a message was sent? That a message was received? Something else?

3

That socket is really subscribing a channel.

For example,

def join("test", %{"id" => id}, socket) do
  :ok = TestWeb.Endpoint.subscribe("id:#{id}")
  {:ok, socket}
end

I want to know I didn’t forget subscribing “id:#{id}” on test.

4

Hmmm, usually I would assert that a message that is sent to the "id:#{id}" topic is received by the test process. Perhaps you could create a helper that will assert that the a test-specific message is received.

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