IConfiguration and IConfigurationSection mocking (Microsoft.Extensions.Configuration)

[Rik Svendsen Rose]

Hi

The "new" Microsoft.Extensions.Configuration with IConfiguration and IConfigurationSection samed easy enough to mock. But something wierd happends:

var configuration = Substitute.For<IConfiguration>();

var section = Substitute.For<IConfigurationSection>();

 configuration.GetSection("Assets:Xzy").Returns(_sections);

_sections.Get<Asset[]>().Returns(assets);

But i get this, that i find very very strainght forward. Hav i gone blind, of have i made a weird mistake?:

Can not return value of type Asset[] for IDisposable.Dispose (expected type Void).

Make sure you called Returns() after calling your substitute (for example: mySub.SomeMethod().Returns(value)),

and that you are not configuring other substitutes within Returns() (for example, avoid this: mySub.SomeMethod().Returns(ConfigOtherSub())).

If you substituted for a class rather than an interface, check that the call to your substitute was on a virtual/abstract member.

Return values cannot be configured for non-virtual/non-abstract members.

Correct use:

mySub.SomeMethod().Returns(returnValue);

Potentially problematic use:

mySub.SomeMethod().Returns(ConfigOtherSub());

Instead try:

var returnValue = ConfigOtherSub();

mySub.SomeMethod().Returns(returnValue);

[David Tchepak]

Hello,

Just to clarify, is `_sections` in your example code meant to be `section`? If `_sections` is not an `IConfigurationSection` that could be the problem.

Is this happening when a single test is run? Or is this only when a whole fixture/series of fixtures runs?

If it only happens with multiple tests then I think it is worth trying the beta Analyzers package: https://www.nuget.org/packages/NSubstitute.Analyzers.CSharp/

If you add that to your test project it can pick up some potential problems with non-virtual members in previous tests that could be breaking the test you have shown.

Please let me know how you go.

Regards,

David

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[Rik Svendsen Rose]

 

Should have been: 

configuration.GetSection("Assets:Xzy").Returns(sections);

sections.Get<Asset[]>().Returns(assets); 

Typo in example here, not in code... Code uses _sections and _configuration private fields everywhere :-)

[David Tchepak]

I guessed so, just wanted to check. ;)

Let me know how you go with the Analysers and single vs multiple tests.

--

[kévin]

Hello,

I'm facing the same issue, any update on this ?

Thx,

kévin

[David Tchepak]

Hi kévin,

Are you finding this happening when a single test is run? Or only when a whole fixture or series of fixtures runs?

Has the Analyzers package picked up any issues with the test suite?

Regards,

David

[Max Onger]

For future people reading this, you should substitute the value of the section and not the section itself.

Bad:

conf.GetSection("bla").Returns("bla");

Good:

conf.GetSection("bla").Value.Returns("bla");

It should be enough to once call:

var conf = Substitute.For<IConfiguration>();

and then substitute every value you need, just like above.

Im pretty sure you can cascade it like this too:

conf.GetSection("bla").GetSection("bla").GetSection("bla").Value.Returns("bla");

[Priyankar Dutta]

Did you ever manage to solve this problem?

[Rik Svendsen Rose]

I have not tested. Moved on to something else.

I Will try to find time

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