# Real-Time Phoenix: ProductChannelTest - undefined function describe/2 (pg 203)

**URL:** <https://forum.devtalk.com/t/real-time-phoenix-productchanneltest-undefined-function-describe-2-pg-203/40594>\
**Category:** PragProg Customers\
**Tags:** book-real-time-phoenix, question\
**Created:** [14 February 2022 19:09 UTC](https://forum.devtalk.com/t/real-time-phoenix-productchanneltest-undefined-function-describe-2-pg-203/40594 "2022-02-14T19:09:53Z")\
**Posts on this page:** 7\
**Page:** 1

<div class="post-metadata">

**Author:** ![taguniversalmachine](https://forum.devtalk.com/user_avatar/forum.devtalk.com/taguniversalmachine/32/3274_2.png) [@taguniversalmachine](https://forum.devtalk.com/u/taguniversalmachine)\
**Post date:** [14 February 2022 19:09 UTC](https://forum.devtalk.com/t/real-time-phoenix-productchanneltest-undefined-function-describe-2-pg-203/40594/1 "2022-02-14T19:09:53Z")

</div>

Hi,

I am getting an error I cannot figure out on my test.  
I have what I think is the exact code from the book, other than I changed “use” to “import” to fix a deprecation warning:

```auto
defmodule Sneakers23Web.ProductChannelTest do

  #use Sneakers23Web.ChannelCase, async: true
  import Sneakers23Web.ChannelCase
  alias Sneakers23Web.{Endpoint, ProductChannel}
  alias Sneakers23.Inventory.CompleteProduct

  describe "notify product released" do
    test "the size selector for the product is broadcast" do
      {inventory, _data} = Test.Factory.InventoryFactory.complete_products()
      [_, product] = CompleteProduct.get_complete_products(inventory)

      topic = "product:#{id}"
      Endpoint.subscribe(topic)

      ProductChannel.notify_product_released(product)

      assert_broadcast "released", %{size_html: html}

      assert html =~ "size-container__entry"

      Enum.each(product.items, fn item ->
        assert html =~ ~s(value="#{item.id}")
      end)
    end
  end
end

```

The error I get is:

> sneakers\_23 % mix test
> 
> 12:57:13.705 [info] Migrations already up  
> …  
> == Compilation error in file test/sneakers\_23\_web/product\_channel\_test.exs ==  
> \*\* (CompileError) test/sneakers\_23\_web/product\_channel\_test.exs:8: undefined function describe/2  
> (stdlib 3.15.2) erl\_eval.erl:685: :erl\_eval.do\_apply/6  
> (elixir 1.12.1) lib/kernel/parallel\_compiler.ex:428: Kernel.ParallelCompiler.require\_file/2  
> (elixir 1.12.1) lib/kernel/parallel\_compiler.ex:321: anonymous fn/4 in Kernel.ParallelCompiler.spawn\_workers/7

I can imagine why describe would not show up if I am not importing the right test module, but why is it saying I have describe/2 when I am clearly only giving it one argument? Changing import back to use doesn’t fix anything either.

---

<div class="post-metadata">

**Author:** ![sb8244](https://forum.devtalk.com/user_avatar/forum.devtalk.com/sb8244/32/209_2.png) [@sb8244](https://forum.devtalk.com/u/sb8244)\
**Post date:** [14 February 2022 19:41 UTC](https://forum.devtalk.com/t/real-time-phoenix-productchanneltest-undefined-function-describe-2-pg-203/40594/2 "2022-02-14T19:41:11Z")

</div>

Hi, you must `use` the ChannelCase because that brings in the macros and other functions required.

What error do you get when you `use` it?

---

<div class="post-metadata">

**Author:** ![taguniversalmachine](https://forum.devtalk.com/user_avatar/forum.devtalk.com/taguniversalmachine/32/3274_2.png) [@taguniversalmachine](https://forum.devtalk.com/u/taguniversalmachine)\
**Post date:** [14 February 2022 20:16 UTC](https://forum.devtalk.com/t/real-time-phoenix-productchanneltest-undefined-function-describe-2-pg-203/40594/3 "2022-02-14T20:16:57Z")

</div>

If I do `use` I get the deprecation warning about use, and a slightly different error, it doesn’t find test/2:

Here is the entire module:

```auto
defmodule Sneakers23Web.ProductChannelTest do

  use Sneakers23Web.ChannelCase, async: true
  #import Sneakers23Web.ChannelCase
  alias Sneakers23Web.{Endpoint, ProductChannel}
  alias Sneakers23.Inventory.CompleteProduct

  describe "notify product released" do
    test "the size selector for the product is broadcast" do
      {inventory, _data} = Test.Factory.InventoryFactory.complete_products()
      [_, product] = CompleteProduct.get_complete_products(inventory)

      topic = "product:#{product.id}"
      Endpoint.subscribe(topic)

      ProductChannel.notify_product_released(product)

      assert_broadcast "released", %{size_html: html}

      assert html =~ "size-container__entry"

      Enum.each(product.items, fn item ->
        assert html =~ ~s(value="#{item.id}")
      end)
    end
  end
end

```

running the test:

> mix test
> 
> 14:09:08.826 [info] Migrations already up  
> …warning: Using Phoenix.ChannelTest is deprecated, instead of:
> 
> ```
> use Phoenix.ChannelTest
> 
> ```
> 
> do:
> 
> ```
> import Phoenix.ChannelTest
> 
> ```
> 
> test/sneakers\_23\_web/product\_channel\_test.exs:3: Sneakers23Web.ProductChannelTest (module)
> 
> …  
> == Compilation error in file test/sneakers\_23\_web/views/error\_view\_test.exs ==  
> \*\* (CompileError) test/sneakers\_23\_web/views/error\_view\_test.exs:17: undefined function test/2  
> (stdlib 3.15.2) erl\_eval.erl:685: :erl\_eval.do\_apply/6  
> (elixir 1.12.1) lib/kernel/parallel\_compiler.ex:428: Kernel.ParallelCompiler.require\_file/2  
> (elixir 1.12.1) lib/kernel/parallel\_compiler.ex:321: anonymous fn/4 in Kernel.ParallelCompiler.spawn\_workers/7

These are the libraries I am using:

```auto
defp deps do
    [
      {:phoenix, "~> 1.6.0"},
      {:phoenix_pubsub, "~> 2.0.0"},
      {:phoenix_ecto, "~> 4.4.0"},
      {:ecto_sql, "~> 3.7.2"},
      {:postgrex, ">= 0.0.0"},
      {:phoenix_html, "~> 3.2.0"},
      {:phoenix_live_reload, "~> 1.3.3", only: :dev},
      {:gettext, "~> 0.11"},
      {:jason, "~> 1.0"},
      {:plug_cowboy, "~> 2.0"}
    ]
  end

```

---

<div class="post-metadata">

**Author:** ![sb8244](https://forum.devtalk.com/user_avatar/forum.devtalk.com/sb8244/32/209_2.png) [@sb8244](https://forum.devtalk.com/u/sb8244)\
**Post date:** [14 February 2022 20:28 UTC](https://forum.devtalk.com/t/real-time-phoenix-productchanneltest-undefined-function-describe-2-pg-203/40594/4 "2022-02-14T20:28:42Z")

</div>

Ah, open up `test/support/channel_case.ex` and change the code there. You’ll see `use Phoenix.ChannelTest` is currently there.

You are likely using the newest Phoenix. There aren’t a ton of differences, but some minor things may pop up, like PubSub setup. If you pin the Phoenix version, you’ll get things working for sure.

---

<div class="post-metadata">

**Author:** ![taguniversalmachine](https://forum.devtalk.com/user_avatar/forum.devtalk.com/taguniversalmachine/32/3274_2.png) [@taguniversalmachine](https://forum.devtalk.com/u/taguniversalmachine)\
**Post date:** [14 February 2022 22:27 UTC](https://forum.devtalk.com/t/real-time-phoenix-productchanneltest-undefined-function-describe-2-pg-203/40594/5 "2022-02-14T22:27:20Z")

</div>

Ok so I changed the use to import in channel\_case.ex but no difference.  
I had initially updated to phoenix-1.6 because I am working through a few different books and wanted them all to be on the latest version for my own sanity but also I thought it would be useful to learn how to upgrade a project, but if I give up on that notion and set the versions to what they were, I get af PubSub configuration error

> \*\* (Mix) Could not start application sneakers\_23: Sneakers23.Application.start(:normal, ) returned an error: shutdown: failed to start child: Sneakers23Web.Endpoint  
> \*\* (EXIT) shutdown: failed to start child: Phoenix.PubSub.PG2  
> \*\* (EXIT) shutdown: failed to start child: Phoenix.PubSub.PG2Server  
> \*\* (EXIT) an exception was raised:  
> \*\* (UndefinedFunctionError) function :pg2.create/1 is undefined or private  
> (kernel 8.0.2) :pg2.create({:phx, Sneakers23.PubSub})  
> (phoenix\_pubsub 1.1.2) lib/phoenix/pubsub/pg2\_server.ex:43: Phoenix.PubSub.PG2Server.init/1  
> (stdlib 3.15.2) gen\_server.erl:423: :gen\_server.init\_it/2  
> (stdlib 3.15.2) gen\_server.erl:390: :gen\_server.init\_it/6  
> (stdlib 3.15.2) proc\_lib.erl:226: :proc\_lib.init\_p\_do\_apply/3

which I think was the reason I upgraded everything in the first place because this [post](https://elixirforum.com/t/cannot-start-app-after-update-with-erlang-24/39708)

---

<div class="post-metadata">

**Author:** ![sb8244](https://forum.devtalk.com/user_avatar/forum.devtalk.com/sb8244/32/209_2.png) [@sb8244](https://forum.devtalk.com/u/sb8244)\
**Post date:** [15 February 2022 16:32 UTC](https://forum.devtalk.com/t/real-time-phoenix-productchanneltest-undefined-function-describe-2-pg-203/40594/6 "2022-02-15T16:32:34Z")

</div>

Ah, that’s due to the Erlang version. You are right to upgrade it if you’re following with other books.

I’m unsure of the problem you’re facing because `changed the use to import in channel_case.ex but no difference` is not correct. When you change from `use` to `import` there, that warning will disappear.

I’m unable to provide updated code for the book because that has to go through a process with the publisher. I’m willing to evaluate my options for providing a code-update, but I need to get their thoughts here.

What about this: you upload your warning code (not the one with :pg2 failing) to Github and I’ll update it to work with latest Erlang/Elixir without warnings. I cannot do every chapter’s code, but I can do it for the current code you’re stuck on. It is likely something you can then apply to other chapters.

---

<div class="post-metadata">

**Author:** ![taguniversalmachine](https://forum.devtalk.com/user_avatar/forum.devtalk.com/taguniversalmachine/32/3274_2.png) [@taguniversalmachine](https://forum.devtalk.com/u/taguniversalmachine)\
**Post date:** [16 February 2022 06:24 UTC](https://forum.devtalk.com/t/real-time-phoenix-productchanneltest-undefined-function-describe-2-pg-203/40594/7 "2022-02-16T06:24:45Z")

</div>

Hmm well everything seems to be working now, I did change the PubSub config as suggested by the compiler and the `use` to `import` in the macro . I was getting some other weird errors but I deleted \_build and recompiled and that seemed to fix it, so I guess no action is required, thanks!

> **[GitHub - taguniversalmachine/sneakers\_23](https://github.com/taguniversalmachine/sneakers_23)**
>
> Contribute to taguniversalmachine/sneakers\_23 development by creating an account on GitHub.

Commit: cda002dc4b8cb339699cbb7e74d821ed1e558039

Edit: I think this was all caused by my having two installs of Elixir, at some point while working on a different project I installed asdf and didn’t uninstall the original eliixir, which might explain why the \_build directory was in an inconsistent state.  
So you are right, it was due to erlang version conflict and not the code’s fault.