public void AttachToSession_ShouldReturnRight_WhenIdIsValid()
{
var entry = new Entry("hello", null, null, _clock);
_dbContext.Entries.Add(entry);
_dbContext.SaveChanges();
var session = _sut.NewSession();
var result = _sut.AttachToSession(entry, session.Id);
result.IsRight.Should().BeTrue();
entry.Session.Should().NotBeNull();
_dbContext.Sessions.Find(session.Id).Entries.Should().NotBeEmpty();
}