Default value (object of type Proxy) can give false positives when testing validations

Hi,
Thanks for an amazing lib! It definitely makes work with JavaScript more human-friendly! :)
I've bumped into a small difference with NSubstitute behaviour and wondering if maybe I just can't find a proper syntax to turn on or off a setting to make things work similarly to what I used to in C#:)

So what I'm trying to achieve.
I have an interface

interface Worker {
   SUPPORTED_WORK: number[];
   doSomething();
}

And this kind of usage of the interface in some service:

constructor (private worker: Worker) {}
....

public someServiceMethod(workId) {
   if (!this.worker.SUPPORTED_WORK.includes(workId)) {
      throw Error("Invalid work");
   }
...

Currently, when I setup a test to cover this validation, if I don't specifying any behaviour for SUPPORTED_WORK property, the test automatically passes.

const worker = Substitute.for<Worker>();
const service = new MyService(worker);

service.someServiceMethod(42);
...//some test logic

Basing on the NSubstitute behaviour, I would expect this usage to throw an error, since the SUPPORTED_WORK property is missing or .include behaviour returns null or something like that by default.

At the moment, if the mock is unset .include(workId) returns a Proxy object, which is truthy. It makes the if-statement pass and giving a false positive in my test.
Even if I wrap this check into some method like:

   if (!this.worker.isWorkSupported(workId)) {
      throw Error("Invalid work");
   }

The issue remains.

Wondering, if I can just tweak some setting to prevent false positives in that kind of checks when I miss to setup returns of my mock?

@SergiiVolodkoWorking

Hi @SergiiVolodkoWorking
Thanks for the detailed issue report!
Due to javascript limitations, you need to setup the mock to return false (to make your example work).
If we threw everytime a function or property of a mock is called, we wouldn't be able to record that execution -> no assertions possible (received, didNotReceive, ...).
And we need to return a proxy in order to handle the mock functions:

worker.isWorkSupported(Arg.any()).returns(true) // if worker.isWorkSupported() returned null, a TypeError would be thrown

If you had any ideas how this could change / improve, we are happy to hear suggestions and feedback

@ffMathy

The only workaround I can think of, is implementing a custom Symbol.toPrimitive function.
That should cast the proxy into 0, '' or null(or undefined?).
What do you think @ffMathy ?

Hmm not sure what you mean here. Can you elaborate? 😅🙏

Hmm I think it was late last night and I was sleepy 😪
I somehow missed that .toPrimitive only works for some of the unary operators

Navigation Menu

Repository navigation

Default value (object of type Proxy) can give false positives when testing validations #165

Metadata

Assignees

Labels

Projects

Milestone

Relationships

Development

Default value (object of type Proxy) can give false positives when testing validations #165

Description

Activity

notanengineercom commented on Jan 15, 2021

notanengineercom commented on Sep 12, 2021

ffMathy commented on Sep 13, 2021

notanengineercom commented on Sep 13, 2021

Metadata

Metadata

Assignees

Labels

Projects

Milestone

Relationships

Development

Issue actions