RE: IQueryable mock throws on ToListAsync()

This issue is related to #32 but there was no resolution given there so I am opening a new issue.

When mocking an IQueryable, I am getting the exception

System.InvalidOperationException : The source IQueryable doesn't implement IAsyncEnumerable<Event>. Only sources that implement IAsyncEnumerable can be used for Entity Framework asynchronous operations.

My code is structured as follows:

// Method Under Test
public async Task<List<Event>> GetEvents(FilterOptions filterOptions)
{
	var queryable = GetEventsQueryable();

	queryable = FilterByDate(queryable, filterOptions);
	// queryable = FilterByLocation(), FilterBy...(), etc

	var events = await queryable
		.ToListAsync()
		.ConfigureAwait(false);

	return events;
}

public IQueryable<Event> GetEventQueryable()
{
	try
	{
		return MyDbContext
			.EventData
			.AsQueryable();
	}
	catch
	{
		...
	}
}

public IQueryable<Event> FilterByDate(
	IQueryable<Event> queryable,
	FilterOptions options)
{
	if (options.StartDate != null)
	{
		queryable = queryable.Where(e => e.EventDate >= options.StartDate);
	}

	if (options.EndDate != null)
	{
		queryable = queryable = queryable.Where(e => e.EventDate <= options.EndDate);
	}

	return queryable;
}

// Test
private List<Event> Events
{
	get
	{
		new List<Event>
		{
			...
		};
	}
}

[Fact]
public void GetEvents_DefaultFilterOptions_ReturnsAllEvents()
{
	// Arrange
	var mockQueryable = Events.AsQueryable().BuildMock();

	var expectedEvents = new List<Event>
	{
		...
	};
	
	...
	mockCaller
		.Setup(m => m.GetEventsQueryable())
		.Returns(mockQueryable);

	mockCaller
		.Setup(m => m.FilterByDate(It.IsAny<IQueryable<Event>>(), It.IsAny<FilterOptions>()))
		.Returns(mockQueryable);

	var eventManager = new EventManager();

	var filterOptions = new EventFilterOptions();

	// Act
	var actualEvents = eventManager.GetEvents(filterOptions);

	// Assert
	Assert.Equal(expectedEvents, actualEvents);
}

When the test gets to the events = await queryable.ToListAsync() line it throws the System.InvalidOperationException.

I am not sure what is going wrong or how to fix the issue. I started looking into using the TestAsyncEnumerableEfCore<Event> class and trying to return this instead of the mocked queryable, but the issue still persisted.

[sstream17]

Thank you! I think I accidentally copied from an older commit, which is why the BuildMock() call was missing. You are correct, the real issue was the missing nullable DateTimes in the mock. Can’t believe it was so simple. Thanks for your help.

[romantitov]

@sstream17 if you change your test like this it will work. Main issue was because FilterByDate does not return mock object because it was wrongly initialized