Re: [go-nuts] Mocking out time.Now "globally"

[David Symonds]

On Thu, Dec 27, 2012 at 9:41 PM, Holger Rapp <sir...@gmx.de> wrote:

> So here is my problem: I can provide an interface to my own code that I can
> mock out and that handles time stuff, but how can I mock out e.g. time.After
> or time.Now, so that the timeout code in net.Conn also works with my
> synthetic time?

You can't mock out time.Now and friends; they are functions. You can,
however, define your own interface, like

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.

[Holger Rapp]

Thanks for the answer.

On Friday, December 28, 2012 6:47:07 AM UTC+1, David Symonds wrote:

On Thu, Dec 27, 2012 at 9:41 PM, Holger Rapp <sir...@gmx.de> wrote:

> So here is my problem: I can provide an interface to my own code that I can
> mock out and that handles time stuff, but how can I mock out e.g. time.After
> or time.Now, so that the timeout code in net.Conn also works with my
> synthetic time?

You can't mock out time.Now and friends; they are functions. You can,
however, define your own interface, like

I understand that. But this won't help me as net.Conn.Read still times out after real seconds because I cannot control this code. And as far as I understand I cannot inject my interface into net somehow, right?

So I think I try to write everything using channels then - I can then control better when and how time is sampled. Is there a io.Reader -> channel construct somewhere in the standard library?

[Kyle Lemons]

net.Conn is an interface as well.  You can provide your own implementation, possibly leveraging net.Pipe or iotest.TimeoutReader.

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[Holger Rapp]

Thanks, I actually went that route and did exactly as you suggested.