Avoid mutating global variables, instead opting for dependency injection. This applies to function pointers as well as other kinds of values.
// BAD
// sign.go
var _timeNow = time.Now
func sign(msg string) string {
now := _timeNow()
return signWithTime(msg, now)
}
// GOOD
// sign.go
type signer struct {
now func() time.Time
}
func newSigner() *signer {
return &signer{
now: time.Now,
}
}
func (s *signer) Sign(msg string) string {
now := s.now()
return signWithTime(msg, now)
}
// BAD
// sign_test.go
func TestSign(t *testing.T) {
oldTimeNow := _timeNow
_timeNow = func() time.Time {
return someFixedTime
}
defer func() { _timeNow = oldTimeNow }()
assert.Equal(t, want, sign(give))
}
// GOOD
// sign_test.go
func TestSigner(t *testing.T) {
s := newSigner()
s.now = func() time.Time {
return someFixedTime
}
assert.Equal(t, want, s.Sign(give))
}
