symbolboxer

symbolboxer

From Ruby to Elixir: Broken test for MessageController (182)

Hi! I believe I’ve found an erratum.

tl;dr: MessageController/create does not add changeset validation errors to the flash, which breaks one of its tests.

On page 182 we write this test:

test "invalid params is rejected", %{conn: conn} do
  conn = post(conn, ~p"/messages/new", %{}) assert html_response(conn, 200) =~
             Plug.HTML.html_escape("can't be blank")
end

Which resulted in this error when I ran it:

1) test POST /messages/new invalid params is rejected (PhoneAppWeb.MessageControllerTest)
     test/phone_app_web/controllers/message_controller_test.exs:34
     Assertion with =~ failed
     code:  assert html_response(conn, 200) =~ Plug.HTML.html_escape("can't be blank")
     left:  "<!DOCTYPE html>\n<html lang=\"en\" class=\"[scrollbar-gutter:stable]\">\n  <head>
     [rest of page truncated]
     right: "can&#39;t be blank"

After some valuable Elixir debugging practice, I believe I have the cause. The test in this case is looking for a “can’t be blank” error somewhere on the page. In MessageController/create, there is code that takes errors and puts them into the flash on line 48. However, that code is never reached because changeset validation happens on line 43 and the error shoots us down to line 55. That error handler doesn’t do anything specifically with the error. It passes the changeset to the view to render, but I don’t see where in the view it would display the error. Thus, the validation error doesn’t appear on the rendered view, and the test can’t find it.

Thanks, and just let me know if I’ve gotten something wrong.

Marked As Solved

sb8244

sb8244

Author of From Ruby to Elixir and Real-Time Phoenix

Thanks for sharing that. I took a look at CoreComponents.input and found the definition was slightly varied. I changed this line:

    # used to be:
    # errors =  if Phoenix.Component.used_input?(field), do: field.errors, else: []
    errors = field.errors

and the test passes. This was a change in the latest implementation of CoreComponents, hence the difference.

Now, to get this test passing without modifying the above line, I had to tweak the test to pass in blank inputs:

    test "invalid params is rejected", %{conn: conn} do
      params = %{message: %{to: "", body: ""}}
      conn = post(conn, ~p"/messages/new", params)

      assert html_response(conn, 200) =~
               Plug.HTML.html_escape("can't be blank")
    end

We can look through the implementation of used_input? to see why this works. By passing in the data, the form.params field contains the input field, so it counts as “used”

Where Next?

Popular Pragmatic Bookshelf topics Top

ianwillie
Hello Brian, I have some problems with running the code in your book. I like the style of the book very much and I have learnt a lot as...
New
lirux
Hi Jamis, I think there’s an issue with a test on chapter 6. I own the ebook, version P1.0 Feb. 2019. This test doesn’t pass for me: ...
New
jskubick
I’m under the impression that when the reader gets to page 136 (“View Data with the Database Inspector”), the code SHOULD be able to buil...
New
jskubick
I found an issue in Chapter 7 regarding android:backgroundTint vs app:backgroundTint. How to replicate: load chapter-7 from zipfile i...
New
brunogirin
When trying to run tox in parallel as explained on page 151, I got the following error: tox: error: argument -p/–parallel: expected one...
New
oaklandgit
Hi, I completed chapter 6 but am getting the following error when running: thread 'main' panicked at 'Failed to load texture: IoError(O...
New
creminology
Skimming ahead, much of the following is explained in Chapter 3, but new readers (like me!) will hit a roadblock in Chapter 2 with their ...
New
rainforest
Hi, I’ve got a question about the implementation of PubSub when using a Phoenix.Socket.Transport behaviour rather than channels. Before ...
New
EdBorn
Title: Agile Web Development with Rails 7: (page 70) I am running windows 11 pro with rails 7.0.3 and ruby 3.1.2p20 (2022-04-12 revision...
New
dachristenson
I’ve got to the end of Ch. 11, and the app runs, with all tabs displaying what they should – at first. After switching around between St...
New

Other popular topics Top

AstonJ
What chair do you have while working… and why? Is there a ‘best’ type of chair or working position for developers?
New
Exadra37
Please tell us what is your preferred monitor setup for programming(not gaming) and why you have chosen it. Does your monitor have eye p...
New
AstonJ
Curious to know which languages and frameworks you’re all thinking about learning next :upside_down_face: Perhaps if there’s enough peop...
New
AstonJ
Continuing the discussion from Thinking about learning Crystal, let’s discuss - I was wondering which languages don’t GC - maybe we can c...
New
PragmaticBookshelf
Create efficient, elegant software tests in pytest, Python's most powerful testing framework. Brian Okken @brianokken Edited by Kat...
New
New
husaindevelop
Inside our android webview app, we are trying to paste the copied content from another app eg (notes) using navigator.clipboard.readtext ...
New
PragmaticBookshelf
Programming Ruby is the most complete book on Ruby, covering both the language itself and the standard library as well as commonly used t...
New
PragmaticBookshelf
Author Spotlight: Peter Ullrich @PJUllrich Data is at the core of every business, but it is useless if nobody can access and analyze ...
New
sir.laksmana_wenk
I’m able to do the “artistic” part of game-development; character designing/modeling, music, environment modeling, etc. However, I don’t...
New

Sub Categories: