Binary search in Ruby

binary_search.rb

def binary_search(array, target)
  return false if array.length == 0

  if array.length == 1
    return true if array.first == target
    return false
  end

  midpoint = array.length / 2
  lower = array[0..midpoint-1]
  middle = array[midpoint]
  upper = array[midpoint+1..-1]

  if target == middle
    return true
  elsif target < middle
    binary_search(lower, target)
  elsif target > middle
    binary_search(upper, target)
  end

end

require "minitest/autorun"

class TestBinarySearch < Minitest::Test
  def setup
    @sorted_array1 = [1,2,3,4,7,8,12,15,17,22,23,35,37,45,46,67,69,99,100]
    @sorted_array2 = [1,2,3,4,7,8,12,15,17,22,23,35,37,45,46,67,69,99]
  end

  def test_works_on_odd_numbered_array
    assert_equal binary_search(@sorted_array1, 3), true
    assert_equal binary_search(@sorted_array1, 5), false
    assert_equal binary_search(@sorted_array1, 12), true
    assert_equal binary_search(@sorted_array1, 69), true
    assert_equal binary_search(@sorted_array1, 70), false
  end

  def test_works_on_even_numbered_array
    assert_equal binary_search(@sorted_array2, 3), true
    assert_equal binary_search(@sorted_array2, 5), false
    assert_equal binary_search(@sorted_array2, 12), true
    assert_equal binary_search(@sorted_array2, 69), true
    assert_equal binary_search(@sorted_array2, 70), false
  end
end