Setting up custom response for exception in Phoenix Application

im writing phoenix application with ecto and have the following snippet in the test

{:ok, data} = Poison.encode(%{email: "[email protected]", password: "mypass"})

conn()
|> put_req_header("content-type", "application/json")
|> put_req_header("accept", "application/json")
|> post(session_path(@endpoint, :create), data)
> json_response(:not_found) == %{}

this throws a Ecto.NoResultsError

i have this defined

defimpl Plug.Exception, for: Ecto.NoResultsError do
  def status(_exception), do: 404
end

but the test still throws Ecto.NoResultsError, Any pointers?

Solution

Let's consider how it works per environment.

In :prod, the default is to render error pages, so you should see a page rendered by YourApp.ErrorView with the status code;
In :dev, the default is to show debug pages, because the majority of times you have an error while building your code. If you want to see the actually rendered error page, you need to set debug_errors: false in your config/dev.exs;
In :test, it works like production but, because you are calling your application from the test, your test will also crash if your application crashes. We are improving this on future versions, where you should be able to write something like:
```
assert_raise Ecto.NoResultsError, fn ->
  get conn, "/foo"
end
{status, headers, body} = sent_response(conn)
assert status == 404
assert body =~ "oops"
```