moq testing with an asynchronous operation does not work

Question

I'm trying to mock test with an asynchronous method but i don't know how to set up the moq test to allow it.

noSQLProvider.Setup(x => x.CreateDocumentAsync(It.IsIn<Uri>(), It.IsAny<object>())).Returns();

the error is telling me:

Usage: ResourceResponse x = await CreatDocumentAsync(...);

an expression tree may not contain a call or invocation that uses optional arguments.

Possible duplicate of [How do I Moq a method that has an optional argument in its signature without explicitly specifying it or using an overload?](http://stackoverflow.com/questions/12957537/how-do-i-moq-a-method-that-has-an-optional-argument-in-its-signature-without-exp) — Liam, Jul 05 '16 at 10:44

Ant P · Accepted Answer · 2016-07-05T10:44:43.913

4

I'm guessing you're using this?

In which case the error message is telling you quite clearly that that method has optional parameters and you need to be explicit about them:

noSQLProvider.Setup(x => x.CreateDocumentAsync(It.IsIn<Uri>(),
                                               It.IsAny<object>(),
                                               It.IsAny<RequestOptions>(),
                                               It.IsAny<bool>())).Returns();

This is a limitation that isn't related to async.

NB - I'm not sure on how It.IsAny comparison behaves for nulls, so you might have to replace It.IsAny<RequestOptions>() with something that explicitly sets up that parameter to be null (which is the default).

edited Jul 05 '16 at 10:44

answered Jul 05 '16 at 10:20

Ant P

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Since you're here, do you know what to put in the .Returns() bit? – Callum Jul 05 '16 at 10:32
1

Whatever you want your mock to return! – Ant P Jul 05 '16 at 10:33
can you give me an example – Callum Jul 05 '16 at 10:48
1

@AntP Afaik `It.IsAny()` works fine for nulls, at least it does for me. – LWood Jul 05 '16 at 10:52
@Callum in your example, you are mocking the method `CreateDocumentAsync` so your `.Returns` could return a new document. – TomDane Apr 04 '19 at 23:35

moq testing with an asynchronous operation does not work

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