Idiomatic way to assert on one of several values in ExUnit

Questions / Help
,
1

Hi everyone.
Does anybody know if there is an idiomatic way of doing a pattern matching on a list of assertions

I am trying to do this.

      assert (case git_short_commit do
        "" -> true
        <<_::8*7>> -> true
        _ -> false
      end)

Thank you.

2

Not sure if this is any better?

assert $git_short_commit == "" or match?(<<_::8*7>>, $git_short_commit)
1 Like
3

I’m not sure it would be useful in this case, but there is the flunk function:
(by the way, what is this “$”? Is it a typo?)

case stuff do
  "" -> assert true
  <<_::8*7>> -> assert true
  _ -> flunk("the variable was not an empty string or a 7 byte binary")
end
4 Likes
4

It’s a PHP variable that made its way into Elixir! :laughing:

1 Like
5 
assert [
    &match?("", &1),
    &match?(<<...>>, &1)
  ]
  |> Enum.map(fn check -> check.(value) end)
  |> Enum.any?(& &1)

This maybe.

1 Like
6

Or switch the assert method around:

case value do
  ... -> :ok
  ... -> :ok
  _ -> flunk "Invalid value"
end
3 Likes
7

I didn’t know flunk.

1 Like
8

you mean like @lud proposed up there?

9

Thank you, This is a beautiful approach.

1 Like
10

This one might be more intention-revealing:

blank? = (git_short_commit == "")
seven_bytes? = match?(<<_::8*7>>, git_short_commit)
assert blank? || seven_bytes?, "git short commits must be 7 bytes long (or blank), got: #{git_short_commit}"
2 Likes
11

I will just do:

  assert valid_commit?(git_short_commit)
...
defp valid_commit?(""), do: true
defp valid_commit?(<<_::8*7>>), do: true
defp valid_commit?(_), do: false
2 Likes
12

The problem with these solutions is that as there are more clauses, it becomes really hard to read.