ruby--ruby/spec/ruby/core/string/comparison_spec.rb

# -*- encoding: utf-8 -*-
require_relative '../../spec_helper'
require_relative 'fixtures/classes'

describe "String#<=> with String" do
  it "compares individual characters based on their ascii value" do
    ascii_order = Array.new(256) { |x| x.chr }
    sort_order = ascii_order.sort
    sort_order.should == ascii_order
  end

  it "returns -1 when self is less than other" do
    ("this" <=> "those").should == -1
  end

  it "returns 0 when self is equal to other" do
    ("yep" <=> "yep").should == 0
  end

  it "returns 1 when self is greater than other" do
    ("yoddle" <=> "griddle").should == 1
  end

  it "considers string that comes lexicographically first to be less if strings have same size" do
    ("aba" <=> "abc").should == -1
    ("abc" <=> "aba").should == 1
  end

  it "doesn't consider shorter string to be less if longer string starts with shorter one" do
    ("abc" <=> "abcd").should == -1
    ("abcd" <=> "abc").should == 1
  end

  it "compares shorter string with corresponding number of first chars of longer string" do
    ("abx" <=> "abcd").should == 1
    ("abcd" <=> "abx").should == -1
  end

  it "ignores subclass differences" do
    a = "hello"
    b = StringSpecs::MyString.new("hello")

    (a <=> b).should == 0
    (b <=> a).should == 0
  end

  it "returns 0 if self and other are bytewise identical and have the same encoding" do
    ("ÄÖÜ" <=> "ÄÖÜ").should == 0
  end

  it "returns 0 if self and other are bytewise identical and have the same encoding" do
    ("ÄÖÜ" <=> "ÄÖÜ").should == 0
  end

  it "returns -1 if self is bytewise less than other" do
    ("ÄÖÛ" <=> "ÄÖÜ").should == -1
  end

  it "returns 1 if self is bytewise greater than other" do
    ("ÄÖÜ" <=> "ÄÖÛ").should == 1
  end

  it "ignores encoding difference" do
    ("ÄÖÛ".force_encoding("utf-8") <=> "ÄÖÜ".force_encoding("iso-8859-1")).should == -1
    ("ÄÖÜ".force_encoding("utf-8") <=> "ÄÖÛ".force_encoding("iso-8859-1")).should == 1
  end

  it "returns 0 with identical ASCII-compatible bytes of different encodings" do
    ("abc".force_encoding("utf-8") <=> "abc".force_encoding("iso-8859-1")).should == 0
  end

  it "compares the indices of the encodings when the strings have identical non-ASCII-compatible bytes" do
    xff_1 = [0xFF].pack('C').force_encoding("utf-8")
    xff_2 = [0xFF].pack('C').force_encoding("iso-8859-1")
    (xff_1 <=> xff_2).should == -1
    (xff_2 <=> xff_1).should ==  1
  end

  it "returns 0 when comparing 2 empty strings but one is not ASCII-compatible" do
    ("" <=> "".force_encoding('iso-2022-jp')).should == 0
  end
end

# Note: This is inconsistent with Array#<=> which calls #to_ary instead of
# just using it as an indicator.
describe "String#<=>" do
  it "returns nil if its argument provides neither #to_str nor #<=>" do
    ("abc" <=> mock('x')).should be_nil
  end

  it "uses the result of calling #to_str for comparison when #to_str is defined" do
    obj = mock('x')
    obj.should_receive(:to_str).and_return("aaa")

    ("abc" <=> obj).should == 1
  end

  it "uses the result of calling #<=> on its argument when #<=> is defined but #to_str is not" do
    obj = mock('x')
    obj.should_receive(:<=>).and_return(-1)

    ("abc" <=> obj).should == 1
  end

  it "returns nil if argument also uses an inverse comparison for <=>" do
    obj = mock('x')
    def obj.<=>(other); other <=> self; end
    obj.should_receive(:<=>).once

    ("abc" <=> obj).should be_nil
  end
end