Time Tested techniques for testing time

time-test.md

You can use an unexported package variable pointing to the time.Now function.

var (
    timeNow   = time.Now
    timeAfter = time.After
)

// ...

type Obj struct{}
func (o Obj) TimeCriticalFunc(d time.Duration) bool {
    // Call timeAfter and timeNow.
}

And in your tests do

func TestTimeCriticalFunc(t *testing.T) {
    timeNow = func() time.Time {
        return myTime // Some time that you need
    }
    // "Redefine" timeAfter etc.
    if !Obj{}.TimeCriticalFunc(10 * 24 * time.Hour) {
        t.Fail()
    }
}