Unit Testing for Extension method using moq

Question

I'm writing a unit test for function uploaddocuments() for azuresearch.

 Unsupported expression: ... =>....Index(It.IsAny<IndexBatch<Document>>(), It.IsAny<SearchRequestOptions>()) Extension methods (here: DocumentsOperationsExtensions.Index) may not be used in setup / verification expressions.

Not sure why it's not working.

code:

    private static async Task uploaddocuments(ISearchIndexClient indexClient)
    {

    var actions = new IndexAction<Hotel>[]
    {

      IndexAction.Upload(
       new Hotel()
       {
           HotelId = "1",
                HotelName = "Secret Point Motel",
                Description = "The hotel is ,

                Rating = 3.6,
                Address = new Address()
                {
                    StreetAddress = "677 5th Ave",
                    City = "New York",
                    StateProvince = "NY",
                    PostalCode = "10022",
                    Country = "USA"
                }

         }
       )
    }
    var batch = IndexBatch.New(actions);
    try
    {
           indexClient.Documents.Index(batch);
    }
    catch (IndexBatchException e)
    {
          console.log(e);
    }
}

Test:

var testMock = new Mock(IDocumentsOperations)();

docOperationsMock.Setup(() => Index(It.IsAny(IndexBatch<Document))(), It.IsAny<SearchRequestOptions)())).Returns(new DocumentIndexResult());


  var mock = new Mock<ISearchIndexClient>()

            .Setup(x => x).Returns(It.IsAny(SearchIndexClient)());

             .SetupGet(a => a.Documents).Returns(It.IsAny("IDocumentsOperations")())

             .Callback(() => IndexBatch.Upload(It.IsAny(IEnumerable(dynamic))()));

            .Returns(testMock.Object);

Answer 1

You can't directly mock static method (eg extension method) with mocking framework.You can use some wrapper to achieve the same. We can not (by default) mock the static call – it's a tight coupling that can not be easily broken.

Here is a very nice article which shows a way to create a wrapper for static method which can help us in this scenario:

http://adventuresdotnet.blogspot.com/2011/03/mocking-static-methods-for-unit-testing.html

Alternatively you can use PEX or MOLES for achieving the same result, you can read it further in below doc:

https://www.microsoft.com/en-us/research/project/pex-and-moles-isolation-and-white-box-unit-testing-for-net/?from=http%3A%2F%2Fresearch.microsoft.com%2Fen-us%2Fprojects%2Fpex%2Fdownloads.aspx

Hope it helps.