Stubbing

Slides

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

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)

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

Never mock the object under test. - Alex

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