JustMock Entity Framework Update Record

Question

I've read through the examples on JustMock (we have the paid version FYI) but am having difficulty in regards to updating a record (not adding).

I have a ILogRepo of

public interface ILogRepo
{
    DbSet<LogEntry> LogEntries { get; }
    LogContext LogContext { get; }
}

I have a LogInteraction of

public class LogInteraction : ILogInteraction
{
    private readonly ILogRepo _logRepo;

    public LogInteraction(ILogRepo logRepo)
    {
        _logRepo = logRepo;
    }

    public void UpdateLog(IList<AckDetail> ackDetails)
    {
        foreach (var ackDetail in ackDetails)
        {
            var logRecord = _logRepo.LogEntries.Single(r => r.CheckNum == ackDetail.CheckNo);
            logRecord.ProcessingStatus = ackDetail.Result.ToString();
            if (!string.IsNullOrWhiteSpace(ackDetail.Message))
            {
                logRecord.Message = ackDetail.Message;
            }
        }
        _logRepo.LogContext.SaveChanges();
    }
}

I've mocked out a fake LogEntries (it's an IList). And last but not least a test of

[TestFixture]
    public class LogTests
    {
        private ILogRepo _mockLogRepo;
        private ILogInteraction _uut;
        private IList<AckDetail> _fakeAckDetails;

        [SetUp]
        public void SetUp()
        {
            //Arrange
            _mockLogRepo = Mock.Create<ILogRepo>();

            _fakeAckDetails = FakeAckDetails();

            _uut = new LogInteraction(_mockLogRepo);
        }

        [Test]
        public void LogUpdated()
        {
            //Arrange
            var expectedResults = FakeLogEntries_AfterAckProcessing();
            var expectedJson = JsonConvert.SerializeObject(expectedResults);

            _mockLogRepo.Arrange(m => m.LogEntries).IgnoreInstance().ReturnsCollection(FakeLogEntries_AfterSending());

            //Act
            _uut.UpdateLog(_fakeAckDetails);
            var actualResults = _mockLogRepo.LogEntries.ToList();
            var actualJson = JsonConvert.SerializeObject(actualResults);

            //Assert
            Assert.AreEqual(expectedResults.Count, actualResults.Count);
            Assert.AreEqual(expectedJson, actualJson);
        }
    }

---

In my test, my _mockLogRepo is not being updated by my LogInteraction. Stepping through the code everything seems all well and good. If I inspect the context though and look for changes, that returns a false though. I think I've matched the example on Telerik's site pretty well, but I've only been able to find info on Adding (and by extrapolating, Removing). But since those two are actual methods and Updating isn't in Entity Framework I'm at a bit of a loss. My code will work in production, but I'd like it to work in Test too (kind of the whole point).