Copeiro

Motivation

Very often we need to iterate and transform results while writing tests and asserting lists. This data manipulation inside test statements becomes a repetitive task as the project grows, demanding extra efforts and sometimes producing bloated tests.

The Copeiro main goal is to extend the ExUnit with an idiomatic DSL that seamless integrates to it, providing a simple way to assert lists of any type.

assert_lists [{:c, 3}, {:a, 1}] in [{:c, 3}, {:b, 2}, {:a, 1}]

Installation

def deps do
  [
    {:copeiro, "~> 0.1.1", only: :test}
  ]
end

Usage

Using Copeiro in a test file

def HelloWorldTest do
  use ExUnit.Case, async: true

  import Copeiro
  # ...
end

Adding Copeiro to your CaseTemplate (recommended)

defmodule MyCase do
  use ExUnit.CaseTemplate

  using do
    quote do
      # This code is injected into every case that calls "use MyCase"
      import Copeiro
    end
  end
end

Examples

For the following examples LEFT and RIGHT will be used to describe the expression:

assert_lists LEFT OPERATOR RIGHT

All elements of LEFT are also elements of RIGHT

iex> assert_lists [1, 2] in [0, 2, 1, 3]
true

iex> assert_lists [{:b, 2}, {:a, 1}] in [{:a, 1}, {:b, 2}, {:c, 3}]
true

LEFT and RIGHT has no element in common

iex> assert_lists [1, 2] not in [3, 4]
true

iex> assert_lists [%{c: 3}, %{d: 4}] not in [%{a: 1}, %{b: 2}]
true

Asserts that two lists match in any order

iex> assert_lists [1, 2, 3] == [2, 1, 3], any_order: true
true

iex> assert_lists [{:a, 0}, {:b, 1}, {:c, 3}] == [{:a, 0}, {:c, 3}, {:b, 1}], any_order: true
true

Asserting lists of maps/structs

When asserting maps and or structs you can compose the expression with keys

iex> assert_lists [%{a: 1}, %{a: 2}] in [%{a: 1, b: 1}, %{a: 2, b: 2}, %{a: 3, b: 3}], keys: [:a]
true

iex> assert_lists [%Person{name: "john", age: 20}] == [%Person{name: "Jane", age: 20}], keys: [:age]
true

Helpful error messages

assert_lists [%{d: 4}, %{a: 1}] not in [%{a: 1}, %{b: 2}]

   match succeeded, but should have failed
   value: %{a: 1}
   left: [%{d: 4}, %{a: 1}]
   right: [%{a: 1}, %{b: 2}]

License

MIT License

Copyright (c) 2021 Felipe Beline Baravieira