public async Task AddAssignment_WithValidationMessages_ReturnsValidationMessages()
        {
            var input = _fixture.Create <AddAssignmentRequest>();
            var expectedValidationMessages = _fixture.CreateMany <ValidationMessage>();

            _assignmentValidator
            .Setup(x => x.ValidateRules(input))
            .Returns(expectedValidationMessages);

            AddAssignmentResult result = await _sut.AddAssignmentAsync(input);

            result.Should().NotBeNull();
            result.ValidationMessages.Should().BeEquivalentTo(expectedValidationMessages);
        }