expr-lang
Allow mockable/predictable now()
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?
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,
})
}
}
}
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.
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Make sense. I will add a helper.
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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.
Mocking time can be done in many ways, it may be hard to replicate every possible use case. Why not just use expr.DisableBuiltin("now"), expr.Function("now", /* your mocking approach here ... */) in your tests?
