Testing flash message from LiveView

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1

I’m trying to test a Phoenix phx-click event which, after being clicked, adds a flash message to the socket of a Live view: put_flash (), and also the Live view updates some of its components (This if I can check it correctly from the test). But when trying to make the assertion with the flash the test fails, because the flash is nil (Although this in practice if it shows.

My handle_event looks something like this:

def handle_event("deactivate", _params, socket) do
    ...

    socket
    |> clear_flash()
    |> put_flash(:info, "Show disabled!")
    |> (&{:noreply, &1}).()
  end

And test:

test "click deactivate button", %{slug: slug, conn: conn} do
      conn =
        conn
           |> ...
           |> get("/show/#{slug}")

      {:ok, view, html} = live(conn, "/show/#{slug}")

      assert html =~ "Active" #The button has this text (pass)
      assert render_click(view, :unsubscribe) =~ "Activate this show" #Components that update after the click (pass)
      assert get_flash(conn, :info) == "Show disabled!" #Flash message (assertion failed)
    end

Test result:

 Assertion with == failed
     code:  assert get_flash(conn, :info) == "Show disabled!"
     left:  nil
     right: "Show disabled!"

Note: The flash that I’m trying to access is in the assigns of the Phoenix.LiveView.Socket

4 Likes
2

Hmm, good question. Have you found something in the meantime?

3

Hello @Euphorichuman,

a) I think you should have an element in the dom that shows the flash message to user?

assert has_element?(view, your_selector_here, maybe_some_text)

b) the flash is indeed in the assigns of view, not in conn
See Phoenix.LiveView.put_flash/3, Phoenix.LiveView.Utils.put_flash/3.
You may want to use :sys.get_state to peek in the state of the view?

I recommend a) over b).

Finally,

c) Phoenix.LiveViewTest — Phoenix LiveView v0.20.2 makes it easy to test a redirect, and the redirect tuple has a flash when there is one…

I understand that is not your case, but it happens the only flash test I have use that.

1 Like
4

if you explicitly call render/1 after render_click/2, you can assert if the returned HTML includes the flash message (which is great, because we avoid testing implementation details):

{:ok, view, html} = live(conn, "/show/#{slug}")

assert html =~ "Active" #The button has this text (pass)
assert render_click(view, :unsubscribe) =~ "Activate this show" #Components that update after the click (pass)
# assert get_flash(conn, :info) == "Show disabled!" #Flash message (assertion failed)
# do this instead 👇
assert render(view) =~ "Show disabled!"

I found this solution here Send event from live component to parent Live View - #6 by MMore

1 Like