Allow mockable/predictable now()

[rossb83]

Its hard to test out programs that rely on time for example:

now().Sub(StartTime) >= 40*duration("24h")

Would it be possible to allow a testing option for now() to give a predictable/settable time?

[antonmedv]

What about a patcher what will replace now with date function calls?

[rossb83]

So yes something like that would do what I want. What about an option like expr.MockNow(time.UnixMilli(1739840603000)) to sort of hide the complexity/boilerplate vs below?

type nowPatcher struct {
	curr time.Time
}

func (p *nowPatcher) Visit(node *ast.Node) {
	if builtinNode, ok := (*node).(*ast.BuiltinNode); ok {
		if builtinNode.Name == "now" {
			ast.Patch(node, &ast.ConstantNode{
				Value: p.curr,
			})
		}
	}
}

[antonmedv]

Make sense. I will add a helper.

[rossb83]

If you agree this is a good idea I can open a PR for your approval.

…

On Tue, Feb 18, 2025 at 3:07 AM Anton Medvedev ***@***.***> wrote: Make sense. I will add a helper. — Reply to this email directly, view it on GitHub <#754 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AARSZC2WDT7M2N4LDZRSDK32QLS3VAVCNFSM6AAAAABXHXEB52VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDMNRUHA4DCOBXGQ> . You are receiving this because you authored the thread.Message ID: ***@***.***> [image: antonmedv]*antonmedv* left a comment (expr-lang/expr#754) <#754 (comment)> Make sense. I will add a helper. — Reply to this email directly, view it on GitHub <#754 (comment)>, or unsubscribe <https://github.com/notifications/unsubscribe-auth/AARSZC2WDT7M2N4LDZRSDK32QLS3VAVCNFSM6AAAAABXHXEB52VHI2DSMVQWIX3LMV43OSLTON2WKQ3PNVWWK3TUHMZDMNRUHA4DCOBXGQ> . You are receiving this because you authored the thread.Message ID: ***@***.***>

[antonmedv]

Sure! Please take a look at already existing patchers: https://github.com/expr-lang/expr/tree/master/patcher and follow similar semantic with naming and etc.