Is there an easy way to stub out time.Now() globally during test?

Question

Part of our code is time sensitive and we need to able to reserve something and then release it in 30-60 seconds etc, which we can just do a time.Sleep(60 * time.Secon

Answer 1

With implementing a custom interface you are already on the right way. I take it you use the following advise from the golang nuts thread you've posted:

---

type Clock interface {
  Now() time.Time
  After(d time.Duration) <-chan time.Time
}

and provide a concrete implementation

type realClock struct{}
func (realClock) Now() time.Time { return time.Now() }
func (realClock) After(d time.Duration) <-chan time.Time { return time.After(d) }

and a testing implementation.

---

^Original

Changing the system time while making tests (or in general) is a bad idea. You don't know what depends on the system time while executing tests and you don't want to find out the hard way by spending days of debugging into that. Just don't do it.

There is also no way to shadow the time package globally and doing that would not do anything more you couldn't do with the interface solution. You can write your own time package which uses the standard library and provides a function to switch to a mock time library for testing if it is the time object you need to pass around with the interface solution that is bothering you.

The best way to design and test your code would probably be to make as much code stateless as possible. Split your functionality in testable, stateless parts. Testing these components separately is much easier then. Also, less side effects means that it is much easier to make the code run concurrently.