(rspec-let-each)

let_each is an ergonomic RSpec helper that spawns context blocks with corresponding lets for each value in an array

a common dilemma I found when writing specs was enumerating all edge cases is DRY and gives good coverage but it requires too much block nesting/boiler plate. Also, contexts written like this are not compatible with lets, without some hackery.

e.g.

[foo,bar].each do |x_local|
  context "with x=#{x_local}" do
    let(:x) { x_local }

    it_behaves_like 'an example'
  end
end

alternatively, let + sample is succint but it gives flakey coverage e.g.

let(:x) { [foo, bar].sample }

it_behaves_like 'an example'

with this helper, we should be able to have the best of both worlds

• same coverage as first example
• compatible with let variables
• same succintness as second example

let_each(:x, 2) { [foo, bar] }

it_behaves_like 'an example'

Using the let_each by itself can lead to some awkward patterns when zipping expectations into the examples. That's why I added a chainable method with, intended for the corresponding expectations, or possibly actions. (The length of all chained withs is assumed to be the same as the parent let_each) now we might write

subject { test_method(x) }

let_each(:x, 2) { [foo, bar] }
  .with(:expected_x) { [foo_expect, bar_expect] }

it { is_expected.to eq(expected_x) }

it can be continually chained, in case we need variables in tripples or quads too, why not.

Add this line to your application's Gemfile typically inside the :test group:

group :test do
  gem 'let_each'
end

let_each is configured to automatically mix into RSpec's example groups when loaded. In some projects, the lib folder is automatically loaded. If not, just add a require for let_each in your test setup.

# spec/spec_helper.rb
require 'let_each'

You can immediately start using let_each inside your describe or context blocks.

You can verify that the helper is loaded correctly by running a simple test:

RSpec.describe "LetEach Integration" do
  let_each(:val, [1, 2])
  
  it "works" do
    expect([1, 2]).to include(val)
  end
end

let_each is tested against and supports:

• Ruby: 2.7, 3.0, 3.1, 3.2, 3.3, 3.4
• RSpec: 3.0 and newer

MIT