ruby--ruby/spec/ruby/core/array/at_spec.rb

require File.expand_path('../../../spec_helper', __FILE__)
require File.expand_path('../fixtures/classes', __FILE__)

describe "Array#at" do
  it "returns the (n+1)'th element for the passed index n" do
    a = [1, 2, 3, 4, 5, 6]
    a.at(0).should == 1
    a.at(1).should == 2
    a.at(5).should == 6
  end

  it "returns nil if the given index is greater than or equal to the array's length" do
    a = [1, 2, 3, 4, 5, 6]
    a.at(6).should == nil
    a.at(7).should == nil
  end

  it "returns the (-n)'th elemet from the last, for the given negative index n" do
    a = [1, 2, 3, 4, 5, 6]
    a.at(-1).should == 6
    a.at(-2).should == 5
    a.at(-6).should == 1
  end

  it "returns nil if the given index is less than -len, where len is length of the array"  do
    a = [1, 2, 3, 4, 5, 6]
    a.at(-7).should == nil
    a.at(-8).should == nil
  end

  it "does not extend the array unless the given index is out of range" do
    a = [1, 2, 3, 4, 5, 6]
    a.length.should == 6
    a.at(100)
    a.length.should == 6
    a.at(-100)
    a.length.should == 6
  end

  it "tries to convert the passed argument to an Integer using #to_int" do
    a = ["a", "b", "c"]
    a.at(0.5).should == "a"

    obj = mock('to_int')
    obj.should_receive(:to_int).and_return(2)
    a.at(obj).should == "c"
  end

  it "raises a TypeError when the passed argument can't be coerced to Integer" do
    lambda { [].at("cat") }.should raise_error(TypeError)
  end

  it "raises an ArgumentError when 2 or more arguments is passed" do
    lambda { [:a, :b].at(0,1) }.should raise_error(ArgumentError)
  end
end