One of RSpec’s strengths is that it provides many ways to write tests, clean tests. When your tests are short and uncluttered, it becomes easier to focus on the expected behavior and not on the details of how the tests are written. RSpec Subjects are yet another shortcut allowing you to write simple straightforward tests.
Consider this code −
class Person
attr_reader :first_name, :last_name
def initialize(first_name, last_name)
@first_name = first_name
@last_name = last_name
end
end
describe Person do
it 'create a new person with a first and last name' do
person = Person.new 'John', 'Smith'
expect(person).to have_attributes(first_name: 'John')
expect(person).to have_attributes(last_name: 'Smith')
end
end
It’s actually pretty clear as is, but we could use RSpec’s subject feature to reduce the amount of code in the example. We do that by moving the person object instantiation into the describe line.
class Person
attr_reader :first_name, :last_name
def initialize(first_name, last_name)
@first_name = first_name
@last_name = last_name
end
end
describe Person.new 'John', 'Smith' do
it { is_expected.to have_attributes(first_name: 'John') }
it { is_expected.to have_attributes(last_name: 'Smith') }
end
When you run this code, you will see this output −
.. Finished in 0.003 seconds (files took 0.11201 seconds to load) 2 examples, 0 failures
Note, how much simpler the second code sample is. We took the one it block in the first example and replaced it with two it blocks which end up requiring less code and are just as clear.