strtime.rb

require 'minitest/autorun'

class Strtime

	def initialize(seconds)
		@seconds = seconds
	end

	def to_s
		raise ArgumentError if @seconds.to_i < 0

		days = @seconds / 86400
		hours = (@seconds % 86400) / 3600
		minutes = (@seconds % 3600) / 60
		seconds = @seconds % 60

		days = if days > 1
			"#{days} days"
		elsif days == 1
			"1 day"
		else
			nil
		end

		hours = if hours > 1
			"#{hours} hours"
		elsif hours == 1
			"1 hour"
		else
			nil
		end

		minutes = if minutes > 1
			"#{minutes} minutes"
		elsif minutes == 1
			"1 minute"
		else
			nil
		end

		seconds = if seconds > 1
			"#{seconds} seconds"
		elsif seconds == 1
			"1 second"
		else
			nil
		end

		[days, hours, minutes, seconds].compact.join(" ")
	end

end

class StrtimeTest < Minitest::Test

	def test_minutes
		assert_equal "", Strtime.new(0).to_s
		assert_equal "1 second", Strtime.new(1).to_s
		assert_equal "5 seconds", Strtime.new(5).to_s
		assert_equal "1 minute", Strtime.new(60).to_s
		assert_equal "1 minute 5 seconds", Strtime.new(65).to_s
		assert_equal "2 minutes", Strtime.new(120).to_s
		assert_equal "2 minutes 1 second", Strtime.new(121).to_s
		assert_equal "2 minutes 2 seconds", Strtime.new(122).to_s
	end

	def test_hours
		assert_equal "1 hour", Strtime.new(3600).to_s
		assert_equal "1 hour 1 second", Strtime.new(3601).to_s
		assert_equal "1 hour 2 seconds", Strtime.new(3602).to_s
		assert_equal "1 hour 1 minute", Strtime.new(3660).to_s
		assert_equal "1 hour 2 minutes", Strtime.new(3720).to_s
		assert_equal "1 hour 1 minute 1 second", Strtime.new(3661).to_s
		assert_equal "1 hour 2 minutes 1 second", Strtime.new(3721).to_s
		# TODO: Add more test cases with mixed units
	end

	def test_days
		assert_equal "1 day", Strtime.new(86400).to_s
		assert_equal "2 days 2 hours 2 minutes 2 seconds", Strtime.new(180122).to_s
		# TODO: Add more test cases with mixed units
	end

	def test_negative_number
		assert_raises ArgumentError do
			Strtime.new(-1).to_s
		end
	end

end