The document discusses injecting a clock to control time in tests. It notes that injecting a clock allows tests to run independently of the actual time, helps test time-based rules, and offers more control over timezones than the default. The document asks how injecting a clock works but does not provide details, and suggests explicitly injecting a mocked or factory-created clock for testing.

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Injecting Clock

2. © 2014 RichRelevance, Inc. All Rights Reserved. Confidential.
Injecting Clock is about

3. © 2014 RichRelevance, Inc. All Rights Reserved. Confidential.
Injecting Clock is about

4. © 2014 RichRelevance, Inc. All Rights Reserved. Confidential.
Injecting Clock is about

5. © 2014 RichRelevance, Inc. All Rights Reserved. Confidential.
Injecting Clock is about

6. © 2014 RichRelevance, Inc. All Rights Reserved. Confidential.
Injecting Clock is about

7. © 2014 RichRelevance, Inc. All Rights Reserved. Confidential.
Why do we care?
• You can write tests that do not depend on
when they are run
– Ward against Daylight Savings transition
• You can write tests for specific timing
conditions
– Test these “after NN hours” rules
• Offers another way of controlling timezone
to be used by some code
– More selective than default time zone

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How does it work?

9. © 2014 RichRelevance, Inc. All Rights Reserved. Confidential.
How does it work?

10. © 2014 RichRelevance, Inc. All Rights Reserved. Confidential.
How does it work?

11. © 2014 RichRelevance, Inc. All Rights Reserved. Confidential.
How does it work?

12. © 2014 RichRelevance, Inc. All Rights Reserved. Confidential.
How do I test?
• Inject a clock explicitly
– Mocked
– From a Clock factory