[LiveTest] LiveView render doesn't happen if the event is handled by included LiveComponent

Today I played with testing LiveViews, super easy and fast testing as a result, big thanks for this feature!

I found one inconsistency but I think it is just because newcomers like me don’t understand how LiveView works under the hood. That is related to events which happen inside the stateful LiveComponent. I’ve created a small example here. As you can see there are two LiveViews: one with component and the other one without it just as an example. There is just a phx-submit event handling.

I used the way where the View is a source of truth of the current state so in LiveComponent’s hande_event/3 callback I just send the message to the view existing process which leads to update of the socket assign in the View’s handle_info/2 callback.

What I expected in the tests for the view with the form component is that when I do

html = page_live
|> element("form")
|> render(submit)

it will call LIveView.render/1 function again as said in the documentation here. I assume that it don’t because the html doesn’t change.

You can see these assertions in this test file. To get the updated html I had to call Phoenix.LiveViewTest.render/1 function explicitly.

I think that is expected behavior, I just wanted to share with experience because it took some time to realize that LiveView won’t be re-rendered by itself. I noticed it when I started splitting my LiveView into components and had the failed test. I suppose that the docs should be updated accordingly.

3 Likes

Thanks a lot. I’ve noticed the same when I extracted a part of a live view into a live component.

I guess it happens because render_submit just triggers the submit event and returns the rendered result.