How to mock DocumentClient CreateDocumentQuery with filters for DocumentDb unit testing?

Question

I am writing unit tests for below piece of code which is using Document client CreateDocumentQuery method with where(filter) conditions.

 var documentQuery = ReadOnlyDocumentClient.CreateDocumentQuery<MyView>(UriFactory.CreateDocumentCollectionUri(Constants.COSMOS_DB_NAME, Constants.MY_VIEW_COL_NAME))
                                                       .Where(w => w.Name== query.Name)
                                                       .Where(w => w.DOB> query.StartDate && w.DOB < query.EndDate)
                                                       .AsDocumentQuery();

query is a command parameter which is an input.

I am using MOQ to mock and I am using below code line to mock

 mockDocumentClient.Setup(s => s.CreateDocumentQuery<MyView>(It.IsAny<Uri>(), It.IsAny<FeedOptions>())).Returns(mockDocumentQuery.Object);

Now, above piece of code only mocks CreateDocumentQuery and when Where conditions are executed I am not getting mock support.

Please suggest how can I mock CreateDocumentQuery with where conditions?

Thanks in advance.

Answer 1

When you mock the CreateDocumentQuery, you also need to mock the IQueryProvider which interacts with the IEnumerable that you expect as the result of the query.

Here's an example:

        // somewhere in your test class
        public interface IFakeDocumentQuery<T> : IDocumentQuery<T>, IOrderedQueryable<T>
        {
        }

        // somewhere in your test method
        var expected = new List<YourType>
        {
            new YourType
            {
                yourField = "yourValue"
            }
        };

        var mockDocumentClient = new Mock<IDocumentClient>();
        var dataSource = expected.AsQueryable();
        var response = new FeedResponse<YourType>(dataSource);
        var mockDocumentQuery = new Mock<IFakeDocumentQuery<YourType>>();

        // the part that gets the work done :)
        var provider = new Mock<IQueryProvider>();
        provider
            .Setup(p => p.CreateQuery<YourType>(It.IsAny<Expression>()))
            .Returns(mockDocumentQuery.Object);
        mockDocumentQuery
            .Setup(q => q.ExecuteNextAsync<YourType>(It.IsAny<CancellationToken>()))
            .ReturnsAsync(response);
        mockDocumentQuery
            .SetupSequence(q => q.HasMoreResults)
            .Returns(true)
            .Returns(false);
        mockDocumentQuery
            .As<IQueryable<YourType>>()
            .Setup(x => x.Provider)
            .Returns(provider.Object);
        mockDocumentQuery
            .As<IQueryable<YourType>>()
            .Setup(x => x.Expression)
            .Returns(dataSource.Expression);
        mockDocumentQuery
            .As<IQueryable<YourType>>()
            .Setup(x => x.ElementType)
            .Returns(dataSource.ElementType);
        mockDocumentQuery
            .As<IQueryable<YourType>>()
            .Setup(x => x.GetEnumerator())
            .Returns(dataSource.GetEnumerator);
        mockDocumentClient
            .Setup(c => c.CreateDocumentQuery<YourType>(It.IsAny<Uri>(), It.IsAny<FeedOptions>()))
            .Returns(mockDocumentQuery.Object);

I hope that helps! :)

Answer 2

You can try following example:

var documentClientMock = new Mock<IDocumentClient>();
var docs = new List<MyView>();//your mock data
documentClientMock.Setup(d => d.CreateDocumentQuery<MyView>(It.IsAny<Uri>(), It.IsAny<FeedOptions>()))
    .Returns((IOrderedQueryable<MyView>) docs.AsQueryable());