Discussion on: Why Choose `let` Over instance variables in RSpec

[Jeremy Friesen]

One of my favorite things in RSpec is to consider how let, subject, describe, and context can help you create specs that "self-document" (as in the formatted out is quite nice). When done well, it means I don't need to write many of the it "something or other" (which can sometimes drift from the spec).

RSpec.describe User do
  describe "#registered?"
    let(:confirmation_status) { true }
    let(:user) { User.new(confirmation_status: confirmation_status) }
    subject(:method_call) { user.registered? }

    context "when no confirmation" do
      let(:confirmation_status) { false }

      it { is_expected.to be_falsey }
    end

    context "with confirmation" do
      let(:confirmation_status) { true }

      it { is_expected.to be_truthy }
    end
  end
end

[Akshay Khot]

Definitely! I like how the tests can be self-documenting and also that RSpec provides a way to print the outcomes in various formats so it reads like a specification document.

[Gustavo Matias]

Curious on how you think about describe vs context. In simple terms, how you decide to use one vs the other in different scenarios?

[Jeremy Friesen]

I choose "describe" for the thing under test (e.g. describe "#call"). And "context" for the conditionals (e.g. context "when given user is logged in").

[Dylan Lacey]

I've always liked this, too! It's one of the reasons I find other testing tools so ... unpleasant.

Especially when there's lots of syntactical punctuation littered around.