Only() not throwing an error when more validation failures are present

[jonmsherman]

FluentValidation version

11.1.2

ASP.NET version

5

Summary

During unit testing, I'm using Only() for a certain property and the test is still passing even when there are multiple validation failures on different properties.

Steps to Reproduce

I used the following example code to reproduce this error:

PersonDto.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace Client.WebService.Tests.Playground
{
    public class PersonDto
    {
        public string FirstName { get; set; }
        public string MiddleName { get; set; }
        public string LastName { get; set; }
    }
}

PersonValidator.cs

using Client.WebService.Common.Services.Interfaces;
using Client.WebService.Features.Athletes.DataAccessors.Interfaces;
using Client.WebService.Features.Athletes.Dtos.Request;
using Client.WebService.Features.Athletes.Persistence.Entities;
using FluentValidation;
using System;
using System.Globalization;
using System.Threading;
using System.Threading.Tasks;

namespace Client.WebService.Tests.Playground
{
    public class PersonValidator : AbstractValidator<PersonDto>
    {


        public PersonValidator()
        {

            RuleFor(command => command.FirstName)
                .NotEmpty()
                .WithMessage("First name is required");

            RuleFor(command => command.MiddleName)
                .NotEmpty()
                .WithMessage("Middle name is required");

            RuleFor(command => command.LastName)
                .NotEmpty()
                .WithMessage("Last name is required");
        }
    }
}

PersonValidatorTests.cs

using FluentValidation.TestHelper;
using Microsoft.VisualStudio.TestTools.UnitTesting;

namespace Client.WebService.Tests.Playground
{
    [TestClass]
    public class PersonValidatorTests
    {
        private readonly PersonValidator _personValidator;
        public PersonValidatorTests()
        {
            _personValidator = new PersonValidator();
        }

        [TestMethod]
        public void Test1()
        {
            // Arrange
            var personDto = new PersonDto()
            {
                FirstName = "",
                MiddleName = "",
                LastName = "Sherman",
            };

            // Act
            var result = _personValidator.TestValidate(personDto);

            // Assert
            result
                .ShouldHaveValidationErrorFor(personDto => personDto.FirstName)
                .WithErrorMessage("First name is required")
                .Only();
        }
    }
}

If you debug this test, you will notice there's a validation error for both first name and middle name, but the test should fail because it's only expecting 1 validation error with that specific error message for FirstName

[JeremySkinner]

Hi @jonmsherman I believe in this case .ShouldHaveValidationErrorFor(x => x.FirstName).WithErrorMessage("First name is required").WithErrorMessage("...").Only() is essentially saying "There should only be 1 error with the message 'First name is required' ", rather than "there should only be 1 total error" and ends up filtering out the other failures.

As there is only 1 error associated with the FirstName property the test passes. The call to ShouldHaveValidationErrorFor(x => x.FirstName).WithErrorMessage("...") has already excluded those failures associated with other properties as they don't match the "WithErrorMessage" criteria

Edit to clarify: So essentially WithErrorMessage seems to act filter here which excludes the others. However the documentation seems to suggest something different should happen.

[JeremySkinner]

Hi @Aleksei-Pankratev-EPAM please could you take a look at this issue and confirm if it's behaving as you'd expect, as it's related to Only? Looking at the docs I think I'd expect it to work as @jonmsherman has explained.

[JeremySkinner]

This should be fixed as of 11.2.1, please update and give it a try.

@Aleksei-Pankratev-EPAM I'd appreciate a retroactive review of the fix (9c0c587). Only would only take into account unmatched failures in the current TestValidationContinuation, but would not consider those in a parent. My solution was to change the TestValidationContinuation to store a reference to its parent, and then Only can check the hierarchy of parents to find unmatched failures.