weird array slice behavior

weird.rb

  def test_slicing_arrays_is_weird
    array = [:peanut, :butter, :and, :jelly]

    assert_equal :peanut, array[0]
    assert_equal :butter, array[1]
    assert_equal :and,    array[2]
    assert_equal :jelly,  array[3]
    
    # this confirms that 4 is an invalid index into the array
    assert_equal nil,  array[4]
    
    assert_equal [], array[0,0]
    assert_equal [], array[1,0]
    assert_equal [], array[2,0]
    assert_equal [], array[3,0]

    # wtf?  4 isn't a valid starting index, why do we get back an array here?
    # However, it appears to be intentional based on the special cases listed here:
    # http://www.ruby-doc.org/core-1.9.3/Array.html#method-i-slice
    assert_equal [], array[4,0]

    assert_equal nil, array[5,0]
    assert_equal nil, array[6,0]
  end