Mocking AutoGenerated DB Indentity Field in Entity Framework 6, DBFirst Project

[GianPiero Bresolin]

Hello, I have successfully mocked out a DBContext so that I can test my Entity Framework implementations, using the following lines:

//Initialize our source of ProductRequest MockedData
            var productRequestMockSet = new ProductRequestMocks();
            var productRequestData = productRequestMockSet.Initialize();

            // Create a DbSet substitute.
            var productRequestDbSet = Substitute.For<DbSet<ProductRequest>, IQueryable<ProductRequest>, IDbAsyncEnumerable<ProductRequest>>()
                                .SetupData(productRequestData);

            //Initialize our Mocked DbContext
            _context = Substitute.For<SOURCINGEntities>();
            _context.ProductRequests.Returns(productRequestDbSet);

However when I add records to the ProductRequests entity, my PK field ID is not been auto incremented as it would if I was using the actual database (The ID field is set to auto increment within SQL).  Is there anyway I can get this behavior to occur using NSubstitute, as some of my newer tests require this?

I have tried adding the [DatabaseGenerated(DatabaseGeneratedOption.Identity)] attribute to my Db Context, but this has no effect. And ideally I would like to avoid changing anything in the EF autogenerated files as they are overwritten every time the DB is refreshed.

Any help would be appreciated.

Kind regards

GianPiero

[David Tchepak]

Hi GianPiero,

I'm not familiar with EF sorry. Maybe try posting on stackoverflow.com?

At a rough guess, if you can hook into the `Add` method, you could try something like:

    var nextId = 1;

    sub.WhenForAnyArgs(x => x.Add(null))

          .Do(x => x.Args<Record>().Id = nextId++)

I'm not sure if that will work in this instance but it might give you some ideas. There is a little more about When..Do here: 

http://nsubstitute.github.io/help/callbacks/#when_called_do_this

Regards,

David

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[GianPiero Bresolin]

Hi David,

So sorry that I haven't responded, my apologies, I didn't seem to subscribed to the response, so I didn't know that you had replied.

Your response looks very promising, I will give it a try tomorrow and let you know what the results are.

Thanks for the help,

GianPiero

[GianPiero Bresolin]

Dear David,

And anyone else who is listening. I went with the following in the end:

quoteDbSet.WhenForAnyArgs(x => x.Add(Arg.Any<Quote>()))

.Do(x => ((Quote)x[0]).QuoteID = quoteDbSet.Count() + 1);

So effectively what I am doing is when any Quote record is passed in to the Add method, increment that object's PK field (QuoteID) by the the count of the quoteDbSet +1.

This allows me to effectively mock out the auto incrementing PK.

Thanks for all your help David.

Kind regards

GianPiero

On Wednesday, 28 October 2015 01:32:10 UTC+2, David Tchepak wrote:

[David Tchepak]

Glad you got it sorted. Thanks for sharing the solution. :)

One minor tweak, you can avoid the cast using the CallInfo.Arg<T>() helper:

.Do(x => x.Arg<Quote>().QuoteID = quoteDbSet.Count() + 1);

You could also try Arg.Do [1], which would look something like this:

quoteDbSet.Add(Arg.Do<Quote>(x => x.QuoteID = quoteDbSet.Count()+1));
I find stubbing calls like that a bit confusing, but it is shorter and gives a bit of type safety to your argument match, so might be worth considering.

Regards,

David

[1]: http://nsubstitute.github.io/help/actions-with-arguments/#performing_actions_with_arguments

[GianPiero Bresolin]

Hey David,

Thanks for the update, definitely cleaner and much appreciated, thanks for sharing once again :)

Kind regards

GianPiero