ruby-on-rails - Rspec 测试可比 <=>

Question

我有一个使用的模型，Comparable并且我已经为此实现了所需的<=>方法。我应该如何测试这个 w/ rspec（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

给定以下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

Grade#<=>根据文档所说，我只是测试它的行为是否正常Object#<=>：

# 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

Answer 2

使用存根进行测试。快速简单。

describe Grade do
  context "<=>" do
    before do
      g1 = Grade.new
      g2 = Grade.new
      g3 = Grade.new
      g1.stub(:sort_key=>1)
      g2.stub(:sort_key=>2)
      g3.stub(:sort_key=>1)
    end

    it "calls sort_key" do
      Grade.any_instance.should_receive(:sort_key)
      g1 < g2
    end

    it "works for comparing" do
      expect{g1<g2}.to be_true
      expect{g2>g1}.to be_true
      expect{g1=g3}.to be_true
    end
  end
end