Hi everyone,
There are two recurrent complaints about ExUnit when writing tests:
1. It does not support grouping
2. It does not allow developers to name nor compose setup
The only way in ExUnit to declare some code as part of a setup is by
declaring a setup block and calling the function inside the block, like
this:
setup context do
{:ok, login_as(context)}
end
I would like to propose improvements for those two issues. I will first
write a proposal including code samples and then we can discuss naming and
implementation details.
## Groups and named setups
The idea is to introduce the group/2 macro and allow atoms to be given to
setup:
defmodule StringTest do
use ExUnit.Case, async: true
group "String.capitalize/2" do
setup :set_test_string
test "capitalizes the first letter", context do
assert "T" <> _ = context.test_string
end
end
group "String.bar/2" do
setup context do
# Regular setups are not going anywhere and will still work
# You may return :ok | keyword | map
end
test "..." do ...
end
def set_test_string(_context) do
%{test_string: "test_string"}
end
end
By using groups, we can now better organize the tests and named setups
allow us to easily share setup logic between groups without relying on
nesting.
Internally, we can consider "setup :some_atom" to be equivalent to:
setup context, do: context |> some_atom()
The group/2 macro will also store the group tag in the test. For example,
you will be able to:
mix test --only group:"String.capitalize/2"
Setups defined in group/2 will only apply to the group. We will also
support @grouptag to set some tags specific to the current group. setup_all
cannot be called inside the group (as setup_all is always per test case).
We won't allow group calls to be nested (we want developers to compose at
the function level and not on nesting/hierarchies).
## Naming
There is one big open question which is: is "group" a good name? I am
personally not a fan. group works fine for grouping at the unit test level
but it does not read nicely when you want to group based on a condition
(for example, group "when name is an atom").
Here are some alternatives: context, testing, group, describe, scenario,
having, etc. I recommend everyone to actually try to write some
pseudo-groups in their tests and see what reads nicely. I would love your
feedback on what you think works nicely. Please include examples. :)
One of my favorite picks is context but we already use context to mean the
data that goes through setup and tests.
## Feedback
Please give us feedback on this proposal. Those features are mostly
straight-forward to implement, the most important aspects are the semantics.
Thank you!
*José Valim*
www.plataformatec.com.br
Skype: jv.ptec
Founder and Director of R&D
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