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# PatrickMcSweeny's solution

## to Clock in the Ruby Track

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Instructions
Test suite
Solution

Implement a clock that handles times without dates.

You should be able to add and subtract minutes to it.

Two clocks that represent the same time should be equal to each other.

For installation and learning resources, refer to the Ruby resources page.

For running the tests provided, you will need the Minitest gem. Open a terminal window and run the following command to install minitest:

``````gem install minitest
``````

If you would like color output, you can `require 'minitest/pride'` in the test file, or note the alternative instruction, below, for running the test file.

Run the tests from the exercise directory using the following command:

``````ruby clock_test.rb
``````

To include color from the command line:

``````ruby -r minitest/pride clock_test.rb
``````

## Source

Pairing session with Erin Drummond https://twitter.com/ebdrummond

## Submitting Incomplete Solutions

It's possible to submit an incomplete solution so you can see how others have completed the exercise.

### clock_test.rb

``````require 'minitest/autorun'
require_relative 'clock'

# Common test data version: 2.3.0 1680779
class ClockTest < Minitest::Test
def test_on_the_hour
# skip
assert_equal "08:00", Clock.new(hour: 8).to_s
end

def test_past_the_hour
skip
assert_equal "11:09", Clock.new(hour: 11, minute: 9).to_s
end

def test_midnight_is_zero_hours
skip
assert_equal "00:00", Clock.new(hour: 24).to_s
end

def test_hour_rolls_over
skip
assert_equal "01:00", Clock.new(hour: 25).to_s
end

def test_hour_rolls_over_continuously
skip
assert_equal "04:00", Clock.new(hour: 100).to_s
end

def test_sixty_minutes_is_next_hour
skip
assert_equal "02:00", Clock.new(hour: 1, minute: 60).to_s
end

def test_minutes_roll_over
skip
assert_equal "02:40", Clock.new(minute: 160).to_s
end

def test_minutes_roll_over_continuously
skip
assert_equal "04:43", Clock.new(minute: 1723).to_s
end

def test_hour_and_minutes_roll_over
skip
assert_equal "03:40", Clock.new(hour: 25, minute: 160).to_s
end

def test_hour_and_minutes_roll_over_continuously
skip
assert_equal "11:01", Clock.new(hour: 201, minute: 3001).to_s
end

def test_hour_and_minutes_roll_over_to_exactly_midnight
skip
assert_equal "00:00", Clock.new(hour: 72, minute: 8640).to_s
end

def test_negative_hour
skip
assert_equal "23:15", Clock.new(hour: -1, minute: 15).to_s
end

def test_negative_hour_rolls_over
skip
assert_equal "23:00", Clock.new(hour: -25).to_s
end

def test_negative_hour_rolls_over_continuously
skip
assert_equal "05:00", Clock.new(hour: -91).to_s
end

def test_negative_minutes
skip
assert_equal "00:20", Clock.new(hour: 1, minute: -40).to_s
end

def test_negative_minutes_roll_over
skip
assert_equal "22:20", Clock.new(hour: 1, minute: -160).to_s
end

def test_negative_minutes_roll_over_continuously
skip
assert_equal "16:40", Clock.new(hour: 1, minute: -4820).to_s
end

def test_negative_hour_and_minutes_both_roll_over
skip
assert_equal "20:20", Clock.new(hour: -25, minute: -160).to_s
end

def test_negative_hour_and_minutes_both_roll_over_continuously
skip
assert_equal "22:10", Clock.new(hour: -121, minute: -5810).to_s
end

skip
clock1 = Clock.new(hour: 10, minute: 0)
assert_equal "10:03", (clock1 + Clock.new(minute: 3)).to_s
end

skip
clock1 = Clock.new(hour: 6, minute: 41)
assert_equal "06:41", (clock1 + Clock.new(minute: 0)).to_s
end

skip
clock1 = Clock.new(hour: 0, minute: 45)
assert_equal "01:25", (clock1 + Clock.new(minute: 40)).to_s
end

skip
clock1 = Clock.new(hour: 10, minute: 0)
assert_equal "11:01", (clock1 + Clock.new(minute: 61)).to_s
end

skip
clock1 = Clock.new(hour: 0, minute: 45)
assert_equal "03:25", (clock1 + Clock.new(minute: 160)).to_s
end

skip
clock1 = Clock.new(hour: 23, minute: 59)
assert_equal "00:01", (clock1 + Clock.new(minute: 2)).to_s
end

skip
clock1 = Clock.new(hour: 5, minute: 32)
assert_equal "06:32", (clock1 + Clock.new(minute: 1500)).to_s
end

skip
clock1 = Clock.new(hour: 1, minute: 1)
assert_equal "11:21", (clock1 + Clock.new(minute: 3500)).to_s
end

def test_subtract_minutes
skip
clock1 = Clock.new(hour: 10, minute: 3)
assert_equal "10:00", (clock1 - Clock.new(minute: 3)).to_s
end

def test_subtract_to_previous_hour
skip
clock1 = Clock.new(hour: 10, minute: 3)
assert_equal "09:33", (clock1 - Clock.new(minute: 30)).to_s
end

def test_subtract_more_than_an_hour
skip
clock1 = Clock.new(hour: 10, minute: 3)
assert_equal "08:53", (clock1 - Clock.new(minute: 70)).to_s
end

def test_subtract_across_midnight
skip
clock1 = Clock.new(hour: 0, minute: 3)
assert_equal "23:59", (clock1 - Clock.new(minute: 4)).to_s
end

def test_subtract_more_than_two_hours
skip
clock1 = Clock.new(hour: 0, minute: 0)
assert_equal "21:20", (clock1 - Clock.new(minute: 160)).to_s
end

def test_subtract_more_than_two_hours_with_borrow
skip
clock1 = Clock.new(hour: 6, minute: 15)
assert_equal "03:35", (clock1 - Clock.new(minute: 160)).to_s
end

def test_subtract_more_than_one_day
skip
clock1 = Clock.new(hour: 5, minute: 32)
assert_equal "04:32", (clock1 - Clock.new(minute: 1500)).to_s
end

def test_subtract_more_than_two_days
skip
clock1 = Clock.new(hour: 2, minute: 20)
assert_equal "00:20", (clock1 - Clock.new(minute: 3000)).to_s
end

def test_clocks_with_same_time
skip
clock1 = Clock.new(hour: 15, minute: 37)
clock2 = Clock.new(hour: 15, minute: 37)
assert clock1 == clock2
end

def test_clocks_a_minute_apart
skip
clock1 = Clock.new(hour: 15, minute: 36)
clock2 = Clock.new(hour: 15, minute: 37)
refute clock1 == clock2
end

def test_clocks_an_hour_apart
skip
clock1 = Clock.new(hour: 14, minute: 37)
clock2 = Clock.new(hour: 15, minute: 37)
refute clock1 == clock2
end

def test_clocks_with_hour_overflow
skip
clock1 = Clock.new(hour: 10, minute: 37)
clock2 = Clock.new(hour: 34, minute: 37)
assert clock1 == clock2
end

def test_clocks_with_hour_overflow_by_several_days
skip
clock1 = Clock.new(hour: 3, minute: 11)
clock2 = Clock.new(hour: 99, minute: 11)
assert clock1 == clock2
end

def test_clocks_with_negative_hour
skip
clock1 = Clock.new(hour: 22, minute: 40)
clock2 = Clock.new(hour: -2, minute: 40)
assert clock1 == clock2
end

def test_clocks_with_negative_hour_that_wraps
skip
clock1 = Clock.new(hour: 17, minute: 3)
clock2 = Clock.new(hour: -31, minute: 3)
assert clock1 == clock2
end

def test_clocks_with_negative_hour_that_wraps_multiple_times
skip
clock1 = Clock.new(hour: 13, minute: 49)
clock2 = Clock.new(hour: -83, minute: 49)
assert clock1 == clock2
end

def test_clocks_with_minute_overflow
skip
clock1 = Clock.new(hour: 0, minute: 1)
clock2 = Clock.new(hour: 0, minute: 1441)
assert clock1 == clock2
end

def test_clocks_with_minute_overflow_by_several_days
skip
clock1 = Clock.new(hour: 2, minute: 2)
clock2 = Clock.new(hour: 2, minute: 4322)
assert clock1 == clock2
end

def test_clocks_with_negative_minute
skip
clock1 = Clock.new(hour: 2, minute: 40)
clock2 = Clock.new(hour: 3, minute: -20)
assert clock1 == clock2
end

def test_clocks_with_negative_minute_that_wraps
skip
clock1 = Clock.new(hour: 4, minute: 10)
clock2 = Clock.new(hour: 5, minute: -1490)
assert clock1 == clock2
end

def test_clocks_with_negative_minute_that_wraps_multiple_times
skip
clock1 = Clock.new(hour: 6, minute: 15)
clock2 = Clock.new(hour: 6, minute: -4305)
assert clock1 == clock2
end

def test_clocks_with_negative_hours_and_minutes
skip
clock1 = Clock.new(hour: 7, minute: 32)
clock2 = Clock.new(hour: -12, minute: -268)
assert clock1 == clock2
end

def test_clocks_with_negative_hours_and_minutes_that_wrap
skip
clock1 = Clock.new(hour: 18, minute: 7)
clock2 = Clock.new(hour: -54, minute: -11513)
assert clock1 == clock2
end

def test_full_clock_and_zeroed_clock
skip
clock1 = Clock.new(hour: 24, minute: 0)
clock2 = Clock.new(hour: 0, minute: 0)
assert clock1 == clock2
end
end``````
``````module BookKeeping
VERSION = 2
end

class Clock
attr_accessor :hours, :minutes
DAY = 24
HOUR = 60
private_constant :DAY, :HOUR

def initialize(hours, minutes)
@hours = hours
@minutes = minutes
rollover_minutes
end

def self.at(hours, minutes)
new(hours, minutes)
end

def to_s
format '%02i:%02i', @hours, @minutes
end

def ==(other)
@hours == other.hours && @minutes == other.minutes
end

def +(other)
@minutes += other
rollover_minutes
self
end

private

def rollover_hours
if @hours.negative?
@hours = DAY - -@hours % DAY
else
@hours -= @hours / DAY * DAY
end
@hours = 0 if @hours == DAY
end

def rollover_minutes
minutes = @minutes
if @minutes.negative?
@minutes = HOUR - -@minutes % HOUR
else
@minutes -= @minutes / HOUR * HOUR
end
@hours += minutes / HOUR
rollover_hours
end
end``````

### What can you learn from this solution?

A huge amount can be learnt from reading other people’s code. This is why we wanted to give exercism users the option of making their solutions public.

Here are some questions to help you reflect on this solution and learn the most from it.

• What compromises have been made?
• Are there new concepts here that I could read more about to develop my understanding?