Equilibrium index code

gistfile1.rb

require 'rubygems'
require 'test/unit'

def equi(list)
  left = 0
  right = list.inject { |x, y| x + y }
  equilibrium_indicies = []

  list.each_with_index do |val, i|
    right -= val
    equilibrium_indicies << i if right == left
    left += val
  end

  unless equilibrium_indicies.empty?
    equilibrium_indicies
  else
    -1
  end
end

class TestEqui < Test::Unit::TestCase

  def test_one
    # should pass
    arr = [ -7, 1, 5, 2, -4, 3, 0 ]
    assert_equal(equi(arr), [ 3, 6 ])
  end

  def test_two
    # should pass
    arr = [ 1, 2, 3, 6, -100, 100, 6 ]
    assert_equal(equi(arr), [ 3 ])
  end

  def test_three
    # should pass
    arr = [ 1, 2, 3, -100, 103 ]
    assert_equal(equi(arr), [ 2 ])
  end

  def test_four
    # should fail
    arr = [ 1, 2, 3, -100, 101 ]
    assert_equal(equi(arr), -1)
  end

  def test_start_one
    # should succeed
    arr = [ 0 ]
    assert_equal(equi(arr), [ 0 ])
  end

  def test_start_two
    # should succeed
    arr = [ 0, 0 ]
    assert_equal(equi(arr), [ 0, 1 ])
  end

end