Conversational Clock Kata

The goal of this code kata is to design a Conversational Clock - a cluster of objects, capable of telling the current system time in a conversational format.

Here are several examples of what the Conversational Clock should tell, depending on the time of the day:

Time	Expected Output
01:00 and 13:00	it's one o'clock
08:07	it's seven past eight
12:00	it's noon
24:00	it's midnight
02:30	it's half past three
14:50	it's ten to three
14:45	it's a quarter to three
13:58	it's almost two o'clock
14:01	it's just after two o'clock

Design

The Conversational Clock should:

• know the current system time
• tell the current time using a conversational format, as described above
• provide an API allowing the Conversational Clock to be:
  • instantiated with any dependencies that it may need, such as new ConversationalClock(new SystemTime())
  • asked for the current time using a parameter-less method, such as clock.currentTime(), responding with a String

Things to consider

• Things like the time, random number generators, etc. are typically outside of our control. So here's the first puzzle: how can we test-drive the design of the Conversational Clock without having to wait with running our tests until a specific time of the day?
  • Have a look at the ConversationalClockTest
  • Note that the Conversational Clock relies on the time reading provided by the SystemTime object.
  • How can you modify the values returned by the SystemTime object? Do you need to change the implementation of the class?
• Now that you can control the time, it's worth noticing that some of the examples of the expected behaviour listed above seem to be easier to implement than others:
  1. Consider starting with making the Clock tell the time on an hour ("it's one o'clock", "it's two o'clock")
  2. Add support for telling the time with a minute precision ("it's seven past eight", "it's fifty three past five")
  3. Make the responses a bit more human: "it's a quarter past three" instead of "it's fifteen past three", "it's midnight" instead of "it's zero o'clock" and so on
  4. Make the Clock tell the time relative to the hour that's "closer" - "it's seven to nine" instead of "it's eight fifty three"
  5. To make things more interesting you can consider adding "fuzzy responses", such as: "it's just after two" instead of "14:01", "it's almost three" instead of "14:58"
• Remember to look for opportunities to refactor both the tests and the Conversational Clock as soon as the tests turn green
• Think about "how much testing is enough"? Do you need to test every single possible hour/minute combination? What's the cost if you do? What are the consequences if you don't?

Resources

You might find those resources useful when experimenting with the kata:

• Dependency Injection: Constructor Injection
• Mocking with Mockito
• Parametrised tests with Zohhak

Have fun!

Jan and the Serenity Team