22 lines
722 B
Ruby
22 lines
722 B
Ruby
# frozen_string_literal: true
|
|
|
|
RSpec.describe Mutant::Util, '.one' do
|
|
let(:first) { instance_double(Object) }
|
|
let(:array) { instance_double(Array, one?: true, first: first) }
|
|
|
|
it 'returns first element' do
|
|
expect(described_class.one(array)).to be(first)
|
|
end
|
|
|
|
it 'fails if the list is empty' do
|
|
expect { described_class.one([]) }
|
|
.to raise_error(described_class::SizeError)
|
|
.with_message('expected size to be exactly 1 but size was 0')
|
|
end
|
|
|
|
it 'fails if the list has more than one element' do
|
|
expect { described_class.one([1, 2]) }
|
|
.to raise_error(described_class::SizeError)
|
|
.with_message('expected size to be exactly 1 but size was 2')
|
|
end
|
|
end
|