Stubbing Slides - Code Like This

Stubbing

sometimes a test needs to trick the code
- to test all cases
- for speed
- for clarity
to stub a method is to replace that method with a block during testing

Stubbing a Mock Clock

normally, Time.now returns the current time
in this test, we want to trick the code into thinking it's a different time
```
midnight = Time.parse("12:00 am")
Time.stub(:now) { midnight }
```
the stub method temporarily replaces a method ("now") with a block ("{ midnight }")
Before stubbing, Time.now returns the actual current time
After stubbing, Time.now returns the fake time (midnight)

Stubbing a Time Machine

since our test has access to the fake time, we can change it at will

so we can pretend an hour passed in just an instant

fake_time = Time.parse("12:00 pm")
Time.stub(:now) { fake_time }
do_something
fake_time += 3600  # number of seconds in an hour
do_something_else

during do_something the code thinks it's noon, but during do_something_else the code thinks it's one o'clock

Test Doubles

stubs are a form of test doubles, aka mock objects
others include mocks, fakes, spies, saboteurs...

Mocking Advice

Never mock the object under test. - Alex

*

Never mock values, sometimes mock entities, but mock services freely. - J.B. Rainsberger

see also http://www.confreaks.com/videos/659-rubyconf2011-why-you-don-t-get-mock-objects

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