TheNoobs.Specification Library in C#: Handling Domain Validations Efficiently

The TheNoobs.Specification library is a powerful C# implementation of the Specification design pattern, offering advanced features for encapsulating complex business rules in a single class. This pattern is commonly used to determine whether an entity satisfies a specific set of conditions. By consolidating business rules in one place, it enhances code readability and manageability, promotes code reuse, and separates responsibilities.

Overview

The Specification design pattern provided by TheNoobs.Specification enables you to create specifications with customizable validation behavior. You can choose between two validation modes: CircuitBreaker and NonCircuitBreaker.

• CircuitBreaker: In this mode, specification validation stops at the first item that does not meet the specification criteria. Only the first validation issue is reported in the output.
• NonCircuitBreaker: In this mode, validation continues for all items in the specification, even if multiple items fail to meet the criteria. This mode ensures a comprehensive validation of the specification.

Getting Started

Creating a CircuitBreaker Specification

using TheNoobs.Specification.Abstractions;
using TheNoobs.Specification.Internals;
using TheNoobs.Specification.UnitTests.Stubs.Entities;

namespace TheNoobs.Specification.UnitTests.Stubs.Specifications.Shareholders
{
    public class CircuitBreakerIsShareholderAbleBeSentSpecification : ISpecification<Shareholder>
    {
        private readonly ISpecification<Shareholder> _specification;
        
        public CircuitBreakerIsShareholderAbleBeSentSpecification()
        {
            _specification = SpecificationFactory<Shareholder>
                .CircuitBreaker()
                .Requires("SH001", "Shareholder last name is required.", s => !string.IsNullOrEmpty(s.LastName))
                .And(s => s.Document != null)
                .WithCodeAndDescription("SH002", "Shareholder document cannot be null.")
                .Build();
        }
        
        public bool IsSatisfiedBy(Shareholder entity, out IEnumerable<IIssue> issues)
        {
            return _specification.IsSatisfiedBy(entity, out issues);
        }
    }
}

Creating a NonCircuitBreaker Specification

using TheNoobs.Specification.Abstractions;
using TheNoobs.Specification.Internals;
using TheNoobs.Specification.UnitTests.Stubs.Entities;

namespace TheNoobs.Specification.UnitTests.Stubs.Specifications.Shareholders
{
    public class NonCircuitBreakerIsShareholderAbleBeSentSpecification : ISpecification<Shareholder>
    {
        private readonly ISpecification<Shareholder> _specification;
        
        public NonCircuitBreakerIsShareholderAbleBeSentSpecification()
        {
            _specification = SpecificationFactory<Shareholder>
                .NonCircuitBreaker()
                .Requires("SH001", "Shareholder last name is required.", s => !string.IsNullOrEmpty(s.LastName))
                .And(s => s.Document != null)
                .WithCodeAndDescription("SH002", "Shareholder document cannot be null.")
                .Build();
        }
        
        public bool IsSatisfiedBy(Shareholder entity, out IEnumerable<IIssue> issues)
        {
            return _specification.IsSatisfiedBy(entity, out issues);
        }
    }
}

Usage

Here's how you can use TheNoobs.Specification library in your unit tests:

[Trait("Category", "UnitTest")]
[Trait("Class", nameof(SpecificationBuilder<Shareholder>))]
public class SpecificationTest
{
    [Fact]
    public void Given_AnInvalidObjectAndACircuitBreakerSpecification_When_ITryToCheckIfIsSatisfied_Then_TheSpecificationShouldNotBeSatisfiedAndOnlyTheFirstIssuesShouldBeReported()
    {
        var shareholder = new Shareholder("Bernardo", new DateTime(1984, 03, 26));
        var specification = new CircuitBreakerIsShareholderAbleBeSentSpecification();

        specification.IsSatisfiedBy(shareholder, out var issues).Should().BeFalse();
        issues.Should().HaveCount(1);
    }

    [Fact]
    public void Given_AnInvalidObjectAndANonCircuitBreakerSpecification_When_ITryToCheckIfIsSatisfied_Then_TheSpecificationShouldNotBeSatisfiedAndAllIssuesShouldBeReported()
    {
        var shareholder = new Shareholder("Bernardo", new DateTime(1984, 03, 26));
        var specification = new NonCircuitBreakerIsShareholderAbleBeSentSpecification();

        specification.IsSatisfiedBy(shareholder, out var issues).Should().BeFalse();
        issues.Should().HaveCountGreaterThan(1);
    }
}

Conclusion

TheNoobs.Specification library simplifies complex business rule validation by encapsulating rules in a unified manner. Whether you prefer the CircuitBreaker or NonCircuitBreaker behavior, this library provides the tools you need to enhance the quality and maintainability of your C# code.

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