require 'rspec'
require './unique_pair'

RSpec.describe UniquePair do
  describe '.unique_pairs' do
    subject { described_class.unique_pairs(input) }

    context 'when an array of numbers is provided' do
      let(:input) { [0, 1, 100, 99, 0, 10, 90, 30, 55, 33, 55, 75, 50, 51, 49, 50, 51, 49, 51] }
      let(:output) { [[1,99], [0,100], [10,90], [49,51], [50,50]] }

      it 'returns all unique pairs which sum up to 100' do
        expect(subject).to match_array output
      end
    end

    context 'when no input is provided' do
      let(:input) { nil }
      let(:output) { [] }

      it 'returns an empty array' do
        expect(subject).to match_array output
      end
    end
  end
end