spec/ruby/core/hash/invert_spec.rb


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require_relative '../../spec_helper'
require_relative 'fixtures/classes'

describe "Hash#invert" do
  it "returns a new hash where keys are values and vice versa" do
    { 1 => 'a', 2 => 'b', 3 => 'c' }.invert.should ==
      { 'a' => 1, 'b' => 2, 'c' => 3 }
  end

  it "handles collisions by overriding with the key coming later in keys()" do
    h = { a: 1, b: 1 }
    override_key = h.keys.last
    h.invert[1].should == override_key
  end

  it "compares new keys with eql? semantics" do
    h = { a: 1.0, b: 1 }
    i = h.invert
    i[1.0].should == :a
    i[1].should == :b
  end

  it "does not return subclass instances for subclasses" do
    HashSpecs::MyHash[1 => 2, 3 => 4].invert.class.should == Hash
    HashSpecs::MyHash[].invert.class.should == Hash
  end

  it "does not retain the default value" do
    h = Hash.new(1)
    h.invert.default.should be_nil
    h[:a] = 1
    h.invert.default.should be_nil
  end

  it "does not retain the default_proc" do
    pr = proc { |h, k| h[k] = [] }
    h = Hash.new(&pr)
    h.invert.default_proc.should be_nil
    h[:a] = 1
    h.invert.default_proc.should be_nil
  end

  it "does not retain compare_by_identity flag" do
    h = { a: 9, c: 4 }.compare_by_identity
    h2 = h.invert
    h2.compare_by_identity?.should == false
  end
end