ruby-on-rails - Rspec 测试比较<=>

Question

我有一个使用 Comparable 的模型我已经实现了所需的 <=>为此的方法。我应该如何使用 rspec 进行测试？ (我知道这不是 TDD，因为我已经实现了该方法)？

class Grade < ActiveRecord::Base
  include Comparable
  def <=>(other)
    self.sort_key <=> other.sort_key
  end
end

Answer 1

鉴于以下 Grade实现:

class Grade
  attr_reader :sort_key
  def initialize(sort_key)
    @sort_key = sort_key
  end
  def <=>(other)
    return nil unless other.respond_to?(:sort_key)
    @sort_key <=> other.sort_key
  end
end

我只是测试一下 Grade#<=>根据 documentation 的内容，行为正常对于 Object#<=>说:

# comparable_grade.spec
describe "Grade#<=>" do

  it "returns 0 when both operands are equal" do
    (Grade.new(0) <=> Grade.new(0)).should eq(0)
  end

  it "returns -1 when first operand is lesser than second" do
    (Grade.new(0) <=> Grade.new(1)).should eq(-1)
  end

  it "returns 1 when first operand is greater than second" do
    (Grade.new(1) <=> Grade.new(0)).should eq(1)
  end

  it "returns nil when operands can't be compared" do
    (Grade.new(0) <=> Grade.new("foo")).should be(nil)
    (Grade.new(0) <=> "foo").should be(nil)
    (Grade.new(0) <=> nil).should be(nil)
  end

  it "can compare a Grade with anything that respond_to? :sort_key" do
    other = double(sort_key: 0)
    (Grade.new(0) <=> other).should eq(0)
  end

end