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 element 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 the 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
end