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. Making tests less readable and increasing the chances of mistakes.

The Copeiro main goal is to extend the ExUnit with an idiomatic DSL that seamless integrates to it.

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

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