CoffeeScript selection sort with tests

selectionsort.coffee

# Destructive selection sort.
# [1, 12, 8, 5].selectionSort()
Array::selectionSort = ->

	# Look forward from each element.
	for num, i in this

		# Find the smallest element in this partition.
		smallest = null
		smallestIndex
		j = i
		while j < @length
			if (smallest is null) or (this[j] < smallest)
				smallest = this[j]
				smallestIndex = j
			j++

		# Swap the smallest index with the "look forward" element.
		[this[i], this[smallestIndex]] = [this[smallestIndex], this[i]]

	# All done!
	return this

########################################################################

# Test setup
assert = console.assert
eq = (a, b) ->
	return false if a.length isnt b.length
	for num, i in a
		return false if num != b[i]
	return true

# Tests
assert eq([].selectionSort(), [])
assert eq([0].selectionSort(), [0])
assert eq([1].selectionSort(), [1])
assert eq([1, 2].selectionSort(), [1, 2])
assert eq([2, 1].selectionSort(), [1, 2])
assert eq([1, 2, 3].selectionSort(), [1, 2, 3])
assert eq([2, 1, 3].selectionSort(), [1, 2, 3])
assert eq([3, 1, 2].selectionSort(), [1, 2, 3])
assert eq([3, 2, 1].selectionSort(), [1, 2, 3])
assert eq([0, 2, 3].selectionSort(), [0, 2, 3])
assert eq([2, 0, 3].selectionSort(), [0, 2, 3])
assert eq([3, 0, 2].selectionSort(), [0, 2, 3])
assert eq([3, 2, 0].selectionSort(), [0, 2, 3])
assert eq([4,3,9,25,25,0,-19,55,43].selectionSort(), [-19,0,3,4,9,25,25,43,55])