ArgumentError by `@enforce_keys` is not catched by `assert_raise`

[schaary]

Environment

• Elixir & Erlang versions (elixir --version):

  
  Erlang/OTP 20 [erts-9.0.4] [source] [64-bit] [smp:8:8] [ds:8:8:10] [async-threads:10] [hipe] [kernel-poll:false] [dtrace]

Elixir 1.5.1

* Operating system: macOS 10.12.5

### Current behavior

I define a struct in a module and I want to enfoce that certain keys have to be specified. So I have a `@enforce_keys` statement:

```elixir
defmodule Foo do

  @enforce_keys [:id, :name]
  defstruct :id, :name, :foo, :bar

end

The test looks like this:

defmodule FooTest do
  use ExUnit.Case

  test "the exception" do
    assert_raised ArgumentError, fn -> 
      %Foo{}
    end
  end

end

$> mix test --trace
** (ArgumentError) the following keys must also be given when building struct Foo: [:id, :name]
    (MyProject) expanding struct: Foo.__struct__/1
    test/foo_test.exs:9: FooTest."test the exception"/1
    (elixir) lib/code.ex:376: Code.require_file/2
    (elixir) lib/kernel/parallel_require.ex:59: anonymous fn/2 in Kernel.ParallelRequire.spawn_requires/5

Expected behavior

I would expect the test runs successfully. When I try the example from https://hexdocs.pm/ex_unit/ExUnit.Assertions.html#assert_raise/2 the test runs successfully. But with @enforce_keys and a test of ArgumentError not.

[josevalim]

All struct errors happen at compile time so indeed they won't be caught at runtime. To put it in other words, the module FooTest does not successfully compile.

[marcdel]

Hi @josevalim, I was wondering if you have opinions about using something like "initializer methods" for this?

I was test driving a similar bit of code and added a new/2 method as a documented way (I think I added a doctest instead in my case) to create a valid %Foo{}.

defmodule FooTest do
  use ExUnit.Case

  test "new/2 creates a valid Foo" do
    %Foo{} = Foo.new(1, "name")
  end
end

defmodule Foo do
  @enforce_keys [:id, :name]
  defstruct :id, :name, :foo, :bar

  def new(id, name) do
    %Foo{id: id, name: name}
  end
end

I was also considering doing something like https://thepugautomatic.com/2015/09/testing-compile-time-exceptions-in-elixir/ to test the enforce_keys explicitly as well, but that seems like overkill in this case?