Develop Reference

FakeItEasy not finding call although its there

I experience some strange problems with FakeItEasy.
Imagine following unit test method:
[TestMethod]
public void DeletePerson_WhenCalled_ThenPersonIsDeleted()
{
const int personId = 24;
var commonParam = new CommonParam();
this.testee.DeletePerson(commonParam, personId );
A.CallTo(() => this.personRepository.DeletePersons(commonParam, new[] {personId }, false)).MustHaveHappened(Repeated.Exactly.Once);
A.CallTo(() => this.personRepository.SaveChanges()).MustHaveHappened(Repeated.Exactly.Once);
}
The testee.DeletePerson-method looks like this:
public ResultatModel DeletePerson(CommonParam commonParam, int personId )
{
this.personRepository.DeletePersons(commonParam, new[] { personId });
this.personRepository.SaveChanges();
}
And the personRepository.DeletePersons (but this one is faked by fakeiteasy...):
public void DeletePersons(CommonParam commonParam, IEnumerable<int> ids, bool hardRemove = false)
{
var persons = Entities.per_person.Where(e => ids.Contains(e.personId)
&& (e.accountId == null || e.accountId == commonParam.AccountId)).ToList();
if (hardRemove)
{
Entities.per_person.RemoveRange(persons);
}
else
{
persons.ForEach(person =>
{
person.geloescht = true;
person.mutationsBenutzer = commonParam.DbIdent;
person.mutationsDatum = DateTime.Now;
});
}
}
This is the reason why the test fails
Test method DataService.Test.PersonServiceTest.DeletePerson_WhenCalled_ThenPersonIsDeleted threw exception:
FakeItEasy.ExpectationException:
Assertion failed for the following call:
RepositoryContract.IPersonRepository.DeletePersons(commonParam: Commons.CommonParam, ids: System.Int32[], hardRemove: False)
Expected to find it exactly once but found it #0 times among the calls:
1: RepositoryContract.IPersonRepository.RequestInfo = Faked Commons.Session.RequestInfo
2: RepositoryContract.IPersonRepository.DeletePersons(
commonParam: Commons.CommonParam,
ids: System.Int32[],
hardRemove: False)
3: RepositoryContract.IPersonRepository.SaveChanges()
Why does the test fail?
Is the new[] { ... } a problem?
Thanks in advance

Is the new[] { ... } a problem?
Yes,
MustHaveHappened(Repeated.Exactly.Once) will "pass" only when mocked method will be called with exact same parameters which you provide in the mock configuration.
A.CallTo(() => this.personRepository.DeletePersons(commonParam, new[] {personId }, false))
.MustHaveHappened(Repeated.Exactly.Once);
For commonParam it works, because you passed same instance to the method under the test.
For new[] {personId } it doesn't work because array given in mock configuration and instance given in the method under the test are different instances of int[].
You can use custom argument matching
A.CallTo(() => this.personRepository.DeletePersons(
commonParam,
A<IEnumerable<int>>.That.Matches(ids => ids.Single() == personId),
false))
.MustHaveHappened(Repeated.Exactly.Once);
Or use more convenience and readable matching for your particular case as Thomas suggested. More convenience matchers

Fabio is correct, but you can make it a bit simpler:
A.CallTo(() => this.personRepository.DeletePersons(
commonParam,
A<IEnumerable<int>>.That.IsSameSequenceAs(personId),
false))
.MustHaveHappened(Repeated.Exactly.Once);

Is the new[] { ... } a problem?
Yes you are right. The new[] creates an array with the type you use between the {...} (It's assumed by the compiler). However your method declaration uses a IEnumerable<int> ids. So basically your test call is calling the wrong/unexisting method, due to signature mismatch.

Right way to return mocked object to tested method

I am writing unit test for my method:
[HttpGet("sani")]
[RequireHttps]
public async Task<IActionResult> GetSuppliersAsync(double latitude, double longitude)
{
if (ModelState.IsValid)
{
var supplierList = new List<Supplier>();
var externalSupplierList = new List<ExternalSupplier>();
try
{
await _supplierRepository.GetSuppliersAsync(supplierList);
await _supplierRepository.GetExternalSupplierAsync(externalSupplierList);
}
catch (Exception)
{
return BadRequest("db");
}
var coll = new Dictionary<dynamic, double>();
AddToCollectionInParallel(supplierList, latitude, longitude, coll);
coll.OrderBy(x => x.Value);
AddExternalToCollectionInParallel(externalSupplierList, latitude, longitude, coll);
return new OkObjectResult(coll.Keys);
}
return BadRequest("model");
}
As you can see, I pass to GetSuppliersAsync() and GetExternalSuppliers() lists, that should be filled there. I do not return lists (so it would be something like: var supplierList = _supplierRepository.GetSuppliersAsync();) because it will be faster to pass object (list) and fill it in method then return list.
So now I want to write an unit test. I am using Xunit for unit tests. My test method:
[Xunit.Fact]
public async Task GetSuppliersAsyncDbTest()
{
var list = new List<Supplier>();
list.Add(new Supplier { SupplierId = "ertre", SupplierName = "test" });
var extList = new List<ExternalSupplier>();
extList.Add(new Models.ExternalSupplier { Id = 4});
_mockRepo.Setup(repo => repo.GetSuppliersAsync(list)).Returns(Task.FromResult(list));
_mockRepo.Setup(repo => repo.GetExternalSuppliersAsync(extList)).Returns(Task.FromResult(extList));
var controller = new SupplierController(_mockRepo.Object);
var result = await controller.GetSuppliersAsync(0.0, 0.0);
var viewResult = Xunit.Assert.IsType<OkObjectResult>(result);
Xunit.Assert.Equal(200, viewResult.StatusCode);
}
My problem is that during unit test, when I call line await _supplierRepository.GetSuppliersAsync(supplierList); it returns empty list, in despite of I've mocked to return list with one item inside. But when I change to var supplierList = _supplierRepository.GetSuppliersAsync(); it returns one item, as expected.
Any ideas how can fix it, or I should just rewrite method to return values as List?

You can do it both ways:
to return by parameter:
var supplierList = new List<Supplier>();
await _supplierRepository.GetSuppliersAsync(supplierList);
use
_mockRepo.Setup(repo => repo.GetSuppliersAsync(It.IsAny<List<Supplier>>()))
.Returns((List<Supplier> x) => {x.AddRange(list); return Task.Delay(0); });
or refactor your code to return lists:
var supplierList = await _supplierRepository.GetSuppliersAsync();
use
_mockRepo.Setup(repo => repo.GetSuppliersAsync())
.Returns(Task.FromResult(list));
There is no performance difference to speak of while returning list so I would advise to refactor your code. It is more clear what is going on that way.

You mocked repository's GetSuppliersAsync() with concrete instance of Supplier list. However in your controller method another instance is used and your stub value is not returned. To fix this you should use argument matcher during mock setup:
_mockRepo.Setup(repo => repo.GetSuppliersAsync(It.IsAny<List<Supplier>>()))
.Returns(Task.FromResult(list));
And how does your repository GetSuppliersAsync() works? Does it alter list passed in parameter or it returns suppliers list? If it's the second case then you should assign the list returned from repository:
supplierList = await _supplierRepository.GetSuppliersAsync(supplierList);
externalSupplierList = await _supplierRepository.GetExternalSupplierAsync(externalSupplierList);

Moq Expression with Constraint ... It.Is<Expression<Func<T, bool>>>

Ok, I am having a hard time trying to figure out how to setup a moq for a method that takes in an expression. There are a lot of examples out there of how to to It.IsAny<>... that is not what I am after. I am after doing with a constraint, so It.Is<>. I have set it up but it never returns the value I have asked it to return.
// Expression being setup
Expression<Func<UserBinding, bool>> testExpression = binding =>
binding.User.Username == "Testing Framework";
// Setup of what expression to look for.
this.bindingManager.Setup(
c => c.GetUserBinding(It.Is<Expression<Func<UserBinding, bool>>>
(criteria => criteria == testExpression)))
.Returns(new List<UserBinding>() { testBinding }.AsQueryable());
// Line of code call from within the class being tested. So this is being mocked and should return the defined object when the same lambda is passed in.
this.bindingManager.GetUserBinding(b => b.User.Username == username)
.SingleOrDefault();
// class under test. So for the test this is being called.
// so this is the method being called and inside this method is where the binding manager is being mocked and called.
var response = this.controller.SendMessage(message, true).Result;
response.StatusCode.Should().Be(HttpStatusCode.BadRequest);
// inside the controller.SendMessage method this method is called with the lambda expression. I have verified the usernames match but when the setup is It.Is this returns null instead of the object setup in the "setup" call.
this.bindingManager.GetUserBinding(b => b.User.Username == username)
.SingleOrDefault();
If I change the setup to It.IsAny... It works and returns the expected object setup in the "returns" method.
I have found a few examples of how to do this on the web one is doing it this way the other is using compile but I can't get that to work either. How do you get this to work for a specific expression?
Update with working solution based on answer
#carlos-alejo got me going in the right direction or at least kicked me back to the Compile action. I was thinking about it wrong. I have the solution working now based on using compile. The key thing to understand about compile is you are giving it an object by which to evaluate/generate the expression for.
So in my case if some one is giving me an expression like this:
binding => binding.User.Username == "Testing Framework";
I need to have a UserBinding like this:
var testBinding = new UserBinding { Binding = new Binding { Name = "Default binding" }, Domain = "test.com", User = new User() { Username = "Testing Framework" } };
I can then create my "setup" call like this:
this.bindingManager.Setup(c => c.GetUserBinding(It.Is<Expression<Func<UserBinding, bool>>>(y => y.Compile()(testBinding))))
.Returns(new List<UserBinding>() { testBinding }.AsQueryable());
This works and in my case returns me back the test binding object as I have setup. If you change the testBinding to be (notice I changed the user name):
var testBinding = new UserBinding { Binding = new Binding { Name = "Default binding" }, Domain = "test.com", User = new User() { Username = "Testing Framework2" } };
It will not work because the code inside my system under test generates an expression looking for "Test Framework"
Maybe it was just me not connecting the dots on this but hopefully it helps others.

It seems that the real problem here is how to compare two lambda expressions, as you try to do in the It.Is<Expression<Func<UserBinding, bool>>> (criteria => criteria == testExpression) clause. Using #neleus's answer to this question, I could come up with this test that actually passes:
readonly Mock<IBindingManager> bindingManager = new Mock<IBindingManager>();
[Test]
public void TestMethod()
{
Expression<Func<string, bool>> testExpression = binding => (binding == "Testing Framework");
bindingManager.Setup(c => c.GetUserBinding(It.Is<Expression<Func<string, bool>>>(
criteria => LambdaCompare.Eq(criteria, testExpression)))).Returns(new List<string>());
var oc = new OtherClass(bindingManager.Object);
var actual = oc.Test(b => b == "Testing Framework");
Assert.That(actual, Is.Not.Null);
bindingManager.Verify(c => c.GetUserBinding(It.Is<Expression<Func<string, bool>>>(
criteria => LambdaCompare.Eq(criteria, testExpression))), Times.Once());
}
Please note the use of the LambdaCompare.Eq static method to compare that the expressions are the same. If I compare the expressions just with == or even Equals, the test fails.

When I was looking for the way to to mock Where() and filter some data,
in code under tests looks like:
Repository<Customer>().Where(x=>x.IsActive).ToList()
I could design such example based on answers form others:
var inputTestDataAsNonFilteredCustomers = new List<Customer> {cust1, cust2};
var customersRepoMock = new Mock<IBaseRepository<Customer>>();
IQueryable<Customer> filteredResult = null;
customersRepoMock.Setup(x => x.Where(It.IsAny<Expression<Func<Customer, bool>>>()))
.Callback((Expression<Func<Customer, bool>>[] expressions) =>
{
if (expressions == null || expressions.Any() == false)
{
return;
}
Func<Customer, bool> wereLambdaExpression = expressions.First().Compile(); // x=>x.isActive is here
filteredResult = inputTestDataAsNonFilteredCustomers.Where(wereLambdaExpression).ToList().AsQueryable();// x=>x.isActive was applied
})
.Returns(() => filteredResult.AsQueryable());
Maybe it will be helpful for feather developers.

Different return values the first and second time with Moq

I have a test like this:
[TestCase("~/page/myaction")]
public void Page_With_Custom_Action(string path) {
// Arrange
var pathData = new Mock<IPathData>();
var pageModel = new Mock<IPageModel>();
var repository = new Mock<IPageRepository>();
var mapper = new Mock<IControllerMapper>();
var container = new Mock<IContainer>();
container.Setup(x => x.GetInstance<IPageRepository>()).Returns(repository.Object);
repository.Setup(x => x.GetPageByUrl<IPageModel>(path)).Returns(() => pageModel.Object);
pathData.Setup(x => x.Action).Returns("myaction");
pathData.Setup(x => x.Controller).Returns("page");
var resolver = new DashboardPathResolver(pathData.Object, repository.Object, mapper.Object, container.Object);
// Act
var data = resolver.ResolvePath(path);
// Assert
Assert.NotNull(data);
Assert.AreEqual("myaction", data.Action);
Assert.AreEqual("page", data.Controller);
}
GetPageByUrl runs twice in my DashboardPathResolver, how can I tell Moq to return null the first time and pageModel.Object the second?

With the latest version of Moq(4.2.1312.1622), you can setup a sequence of events using SetupSequence. Here's an example:
_mockClient.SetupSequence(m => m.Connect(It.IsAny<String>(), It.IsAny<int>(), It.IsAny<int>()))
.Throws(new SocketException())
.Throws(new SocketException())
.Returns(true)
.Throws(new SocketException())
.Returns(true);
Calling connect will only be successful on the third and fifth attempt otherwise an exception will be thrown.
So for your example it would just be something like:
repository.SetupSequence(x => x.GetPageByUrl<IPageModel>(virtualUrl))
.Returns(null)
.Returns(pageModel.Object);

The existing answers are great, but I thought I'd throw in my alternative which just uses System.Collections.Generic.Queue and doesn't require any special knowledge of the mocking framework - since I didn't have any when I wrote it! :)
var pageModel = new Mock<IPageModel>();
IPageModel pageModelNull = null;
var pageModels = new Queue<IPageModel>();
pageModels.Enqueue(pageModelNull);
pageModels.Enqueue(pageModel.Object);
Then...
repository.Setup(x => x.GetPageByUrl<IPageModel>(path)).Returns(pageModels.Dequeue);

Now you can use SetupSequence. See this post.
var mock = new Mock<IFoo>();
mock.SetupSequence(f => f.GetCount())
.Returns(3) // will be returned on 1st invocation
.Returns(2) // will be returned on 2nd invocation
.Returns(1) // will be returned on 3rd invocation
.Returns(0) // will be returned on 4th invocation
.Throws(new InvalidOperationException()); // will be thrown on 5th invocation

You can use a callback when setting up your mock object. Take a look at the example from the Moq Wiki (https://github.com/Moq/moq4/wiki/Quickstart).
// returning different values on each invocation
var mock = new Mock<IFoo>();
var calls = 0;
mock.Setup(foo => foo.GetCountThing())
.Returns(() => calls)
.Callback(() => calls++);
// returns 0 on first invocation, 1 on the next, and so on
Console.WriteLine(mock.Object.GetCountThing());
Your setup might look like this:
var pageObject = pageModel.Object;
repository.Setup(x => x.GetPageByUrl<IPageModel>(path)).Returns(() => pageObject).Callback(() =>
{
// assign new value for second call
pageObject = new PageModel();
});

Adding a callback did not work for me, I used this approach instead http://haacked.com/archive/2009/09/29/moq-sequences.aspx and I ended up with a test like this:
[TestCase("~/page/myaction")]
[TestCase("~/page/myaction/")]
public void Page_With_Custom_Action(string virtualUrl) {
// Arrange
var pathData = new Mock<IPathData>();
var pageModel = new Mock<IPageModel>();
var repository = new Mock<IPageRepository>();
var mapper = new Mock<IControllerMapper>();
var container = new Mock<IContainer>();
container.Setup(x => x.GetInstance<IPageRepository>()).Returns(repository.Object);
repository.Setup(x => x.GetPageByUrl<IPageModel>(virtualUrl)).ReturnsInOrder(null, pageModel.Object);
pathData.Setup(x => x.Action).Returns("myaction");
pathData.Setup(x => x.Controller).Returns("page");
var resolver = new DashboardPathResolver(pathData.Object, repository.Object, mapper.Object, container.Object);
// Act
var data = resolver.ResolvePath(virtualUrl);
// Assert
Assert.NotNull(data);
Assert.AreEqual("myaction", data.Action);
Assert.AreEqual("page", data.Controller);
}

The accepted answer, as well as the SetupSequence answer, handles returning constants.
Returns() has some useful overloads where you can return a value based on the parameters that were sent to the mocked method. Based on the solution given in the accepted answer, here is another extension method for those overloads.
public static class MoqExtensions
{
public static IReturnsResult<TMock> ReturnsInOrder<TMock, TResult, T1>(this ISetup<TMock, TResult> setup, params Func<T1, TResult>[] valueFunctions)
where TMock : class
{
var queue = new Queue<Func<T1, TResult>>(valueFunctions);
return setup.Returns<T1>(arg => queue.Dequeue()(arg));
}
}
Unfortunately, using the method requires you to specify some template parameters, but the result is still quite readable.
repository
.Setup(x => x.GetPageByUrl<IPageModel>(path))
.ReturnsInOrder(new Func<string, IPageModel>[]
{
p => null, // Here, the return value can depend on the path parameter
p => pageModel.Object,
});
Create overloads for the extension method with multiple parameters (T2, T3, etc) if needed.

Reached here for the same kind of problem with slightly different requirement.
I need to get different return values from mock based in different input values and found solution which IMO more readable as it uses Moq's declarative syntax (linq to Mocks).
public interface IDataAccess
{
DbValue GetFromDb(int accountId);
}
var dataAccessMock = Mock.Of<IDataAccess>
(da => da.GetFromDb(It.Is<int>(acctId => acctId == 0)) == new Account { AccountStatus = AccountStatus.None }
&& da.GetFromDb(It.Is<int>(acctId => acctId == 1)) == new DbValue { AccountStatus = AccountStatus.InActive }
&& da.GetFromDb(It.Is<int>(acctId => acctId == 2)) == new DbValue { AccountStatus = AccountStatus.Deleted });
var result1 = dataAccessMock.GetFromDb(0); // returns DbValue of "None" AccountStatus
var result2 = dataAccessMock.GetFromDb(1); // returns DbValue of "InActive" AccountStatus
var result3 = dataAccessMock.GetFromDb(2); // returns DbValue of "Deleted" AccountStatus

We can simply declare one variable with int as a datatype. initialize it to zero, and then increase it's value as follows:
int firstTime = 0;
repository.Setup(_ => _.GetPageByUrl<IPageModel>(path)).Returns(() =>
{
if (firstTime == 0)
{
firstTime = 1;
return null;
}
else if(firstTime == 1)
{
firstTime = 2;
return pageModel.Object;
}
else
{
return null;
}
});

In some cases one needs to have the called function return different types of data based on conditions you cannot impose via the function itself. If the function accepts parameters then those can be used as conditionals to get different data.
In my case, I had a webapi call which I need to mock; earlier it was working out fine based on the input parameter, however one fine day, those parameters were converted to request headers. So since I couldn't provide a callback (no function parameters) so came up with another approach as follows
[Earlier one, when API had parameters]
this.mockedMasterAPICalls.Setup(m => m.GetCountries(It.Is<int>(ou => ou == 2), It.Is<int>(lan => lan == 1))).Returns(Task.FromResult(countryResponse));
[New one, when API had headers... The headers were getting injected into another dictionary of the API caller]
this.mockedMasterAPICalls.Setup(m => m.RequestHeaders).Returns(new Dictionary<string, string>());
this.mockedMasterAPICalls.Setup(m => m.GetCountries()).Returns(() =>
{
if (this.mockedMasterAPICalls.Object.RequestHeaders[GlobalConstants.HeaderOUInstance] == "2")
return Task.FromResult(countryResponse);
else return Task.FromResult(new GetCountryResponse() { Countries = null });
});
Note the use of the mocked object itself to make any decisions required

Verifying a specific parameter with Moq

public void SubmitMessagesToQueue_OneMessage_SubmitSuccessfully()
{
var messageServiceClientMock = new Mock<IMessageServiceClient>();
var queueableMessage = CreateSingleQueueableMessage();
var message = queueableMessage[0];
var xml = QueueableMessageAsXml(queueableMessage);
messageServiceClientMock.Setup(proxy => proxy.SubmitMessage(xml)).Verifiable();
//messageServiceClientMock.Setup(proxy => proxy.SubmitMessage(It.IsAny<XmlElement>())).Verifiable();
var serviceProxyFactoryStub = new Mock<IMessageServiceClientFactory>();
serviceProxyFactoryStub.Setup(proxyFactory => proxyFactory.CreateProxy()).Returns(essageServiceClientMock.Object);
var loggerStub = new Mock<ILogger>();
var client = new MessageClient(serviceProxyFactoryStub.Object, loggerStub.Object);
client.SubmitMessagesToQueue(new List<IMessageRequestDTO> {message});
//messageServiceClientMock.Verify(proxy => proxy.SubmitMessage(xml), Times.Once());
messageServiceClientMock.Verify();
}
I'm starting using Moq and struggling a bit.
I'm trying to verify that messageServiceClient is receiving the right parameter, which is an XmlElement, but I can't find any way to make it work. It works only when I don't check a particular value.
Any ideas?
Partial answer:
I've found a way to test that the xml sent to the proxy is correct, but I still don't think it's the right way to do it.
public void SubmitMessagesToQueue_OneMessage_SubmitSuccessfully()
{
var messageServiceClientMock = new Mock<IMessageServiceClient>();
messageServiceClientMock.Setup(proxy => proxy.SubmitMessage(It.IsAny<XmlElement>())).Verifiable();
var serviceProxyFactoryStub = new Mock<IMessageServiceClientFactory>();
serviceProxyFactoryStub.Setup(proxyFactory => proxyFactory.CreateProxy()).Returns(messageServiceClientMock.Object);
var loggerStub = new Mock<ILogger>();
var client = new MessageClient(serviceProxyFactoryStub.Object, loggerStub.Object);
var message = CreateMessage();
client.SubmitMessagesToQueue(new List<IMessageRequestDTO> {message});
messageServiceClientMock.Verify(proxy => proxy.SubmitMessage(It.Is<XmlElement>(xmlElement => XMLDeserializer<QueueableMessage>.Deserialize(xmlElement).Messages.Contains(message))), Times.Once());
}
By the way, how could I extract the expression from the Verify call?

If the verification logic is non-trivial, it will be messy to write a large lambda method (as your example shows). You could put all the test statements in a separate method, but I don't like to do this because it disrupts the flow of reading the test code.
Another option is to use a callback on the Setup call to store the value that was passed into the mocked method, and then write standard Assert methods to validate it. For example:
// Arrange
MyObject saveObject;
mock.Setup(c => c.Method(It.IsAny<int>(), It.IsAny<MyObject>()))
.Callback<int, MyObject>((i, obj) => saveObject = obj)
.Returns("xyzzy");
// Act
// ...
// Assert
// Verify Method was called once only
mock.Verify(c => c.Method(It.IsAny<int>(), It.IsAny<MyObject>()), Times.Once());
// Assert about saveObject
Assert.That(saveObject.TheProperty, Is.EqualTo(2));

I've been verifying calls in the same manner - I believe it is the right way to do it.
mockSomething.Verify(ms => ms.Method(
It.IsAny<int>(),
It.Is<MyObject>(mo => mo.Id == 5 && mo.description == "test")
), Times.Once());
If your lambda expression becomes unwieldy, you could create a function that takes MyObject as input and outputs true/false...
mockSomething.Verify(ms => ms.Method(
It.IsAny<int>(),
It.Is<MyObject>(mo => MyObjectFunc(mo))
), Times.Once());
private bool MyObjectFunc(MyObject myObject)
{
return myObject.Id == 5 && myObject.description == "test";
}
Also, be aware of a bug with Mock where the error message states that the method was called multiple times when it wasn't called at all. They might have fixed it by now - but if you see that message you might consider verifying that the method was actually called.
EDIT: Here is an example of calling verify multiple times for those scenarios where you want to verify that you call a function for each object in a list (for example).
foreach (var item in myList)
mockRepository.Verify(mr => mr.Update(
It.Is<MyObject>(i => i.Id == item.Id && i.LastUpdated == item.LastUpdated),
Times.Once());
Same approach for setup...
foreach (var item in myList) {
var stuff = ... // some result specific to the item
this.mockRepository
.Setup(mr => mr.GetStuff(item.itemId))
.Returns(stuff);
}
So each time GetStuff is called for that itemId, it will return stuff specific to that item. Alternatively, you could use a function that takes itemId as input and returns stuff.
this.mockRepository
.Setup(mr => mr.GetStuff(It.IsAny<int>()))
.Returns((int id) => SomeFunctionThatReturnsStuff(id));
One other method I saw on a blog some time back (Phil Haack perhaps?) had setup returning from some kind of dequeue object - each time the function was called it would pull an item from a queue.

A simpler way would be to do:
ObjectA.Verify(
a => a.Execute(
It.Is<Params>(p => p.Id == 7)
)
);

I believe that the problem in the fact that Moq will check for equality. And, since XmlElement does not override Equals, it's implementation will check for reference equality.
Can't you use a custom object, so you can override equals?

Had one of these as well, but the parameter of the action was an interface with no public properties. Ended up using It.Is() with a seperate method and within this method had to do some mocking of the interface
public interface IQuery
{
IQuery SetSomeFields(string info);
}
void DoSomeQuerying(Action<IQuery> queryThing);
mockedObject.Setup(m => m.DoSomeQuerying(It.Is<Action<IQuery>>(q => MyCheckingMethod(q)));
private bool MyCheckingMethod(Action<IQuery> queryAction)
{
var mockQuery = new Mock<IQuery>();
mockQuery.Setup(m => m.SetSomeFields(It.Is<string>(s => s.MeetsSomeCondition())
queryAction.Invoke(mockQuery.Object);
mockQuery.Verify(m => m.SetSomeFields(It.Is<string>(s => s.MeetsSomeCondition(), Times.Once)
return true
}