RSpec: Compound Expectations

Question

It's an exercise from a RSpec-course, which I'm currently doing.

Task:

• Create a compound expectation, which asserts the string sportscar starts with the substring "sports" and ends with the substring "car".

• Create a compound expectation, which asserts that the number 30 is even and that it responds to the times method.

• Create a compound expectation, which asserts that the array [2, 4, 8, 16, 32, 64] includes the element 32 and starts with the elements 2, 4, and 8.

My solution:

RSpec.describe "sportscar" do
    it "should start with 'sports' and end with 'car'" do
        expect(subject).to start_with("sports").and end_with("car")
    end

    it "30 is even and responds to the times-method" do
        numb = 30
        expect(numb.even?).to be true and numb.respond_to? :times
    end

    it "shall include 32 and start with the values 2, 4, 8" do
        arr = [2, 4, 8, 16, 32, 64]
        expect(arr).to include(32) and start_with(2, 4, 8)
    end
end

Could it become improved? Perhaps more written in a Ruby-Idiomatic way?

Are my message-strings (it "should start with ..." etc.) done in a good way? Or should it be written in a different way and if so: How?

Answer 1

I don't know what the exercise says exactly but your describe does not match the two last expectations. You should have 3 describes because you describe three different things (a sportscar, number 30 and an array).

RSpec.describe "sportscar" do
    it "should start with 'sports' and end with 'car'" do
        expect(subject).to start_with("sports").and end_with("car")
    end
end

RSpec.describe 30 do
    it "is even and responds to the times-method" do
        numb = 30
        expect(numb.even?).to be true and numb.respond_to? :times
    end
end

RSpec.describe Array do
    it "includes 32 and starts with the values 2, 4, 8" do
        arr = [2, 4, 8, 16, 32, 64]
        expect(arr).to include(32) and start_with(2, 4, 8)
    end
end

This sentence also does not make sense

it 30 is even and responds to the times-method

So it should be something like

it is even and responds to the times-method

I would also not test the implementation but functionality

Instead of responds_to execute the function

count = 0
30.times do { count += 1 }
expect(count).to eq(30)

Generally I would advice to split distinct functionality into it's own it block. and, or etc are usually a sign that there is more than one functionality. Not sure if this is part of the exercise though.

it "should start with 'sports'" do
  expect(subject).to start_with("sports")
end

it "should end with 'car'" do
  expect(subject).to end_with("car")
end

To be fair, all these examples don't feel very natural.