Goodtocode.Assertion

Fluent Assertion aspect-oriented library for .NET Standard 2.0+

Goodtocode.Assertion is a .NET library providing fluent assertion and validation utilities for C# projects. It enables developers to write expressive, readable, and maintainable assertions for business logic, unit tests, and runtime validation. The library is designed for extensibility and can be integrated into any .NET Standard 2.0+ project.

Features

• Fluent assertion syntax for clear, readable code
• Customizable assertion rules and exception handling
• Assertion scopes for grouping related checks
• Lightweight, dependency-free, and compatible with .NET Standard 2.0+
• Designed for use in both production code and unit tests

Quick-Start Steps

1. Clone this repository

   git clone https://github.com/goodtocode/aspect-assertion.git
   

2. Install .NET SDK (latest recommended)

   winget install Microsoft.DotNet.SDK --silent
   

3. Build the solution

   cd src
   dotnet build Goodtocode.Assertion.sln
   

4. Run tests

   cd Goodtocode.Assertion.Tests
   dotnet test
   

Install Prerequisites

• .NET SDK (latest)
• Visual Studio (latest) or VS Code

Top Use Case Examples

1. Basic Assertion Scope

using Goodtocode.Assertion;

int value = 5;
AssertionScope.Begin()
	.Assert(() => value > 0, "Value must be positive.")
	.Assert(() => value < 10, "Value must be less than 10.")
	.End();

2. Validating Object Properties

using Goodtocode.Assertion;

var user = new User { Name = "Alice", Age = 30 };
AssertionScope.Begin()
	.Assert(() => !string.IsNullOrWhiteSpace(user.Name), "Name is required.")
	.Assert(() => user.Age >= 18, "User must be an adult.")
	.End();

3. Custom Validator for Business Logic

using Goodtocode.Assertion;

public class GetMyUsersPaginatedQueryValidator : Validator<GetMyUsersPaginatedQuery>
{
	public GetMyUsersPaginatedQueryValidator()
	{
		RuleFor(v => v.StartDate).NotEmpty()
			.When(v => v.EndDate != null)
			.LessThanOrEqualTo(v => v.EndDate);

		RuleFor(v => v.EndDate)
			.NotEmpty()
			.When(v => v.StartDate != null)
			.GreaterThanOrEqualTo(v => v.StartDate);

		RuleFor(x => x.PageNumber).NotEqual(0);
		RuleFor(x => x.PageSize).NotEqual(0);
	}
}

4. Unit Test Assertion

using Goodtocode.Assertion;
using Microsoft.VisualStudio.TestTools.UnitTesting;

[TestClass]
public class AssertionTests
{
	[TestMethod]
	public void Should_Throw_When_Assertion_Fails()
	{
		Assert.ThrowsException<AssertionFailedException>(() =>
			AssertionScope.Begin()
				.Assert(() => false, "This should fail.")
				.End());
	}
}

Technologies

• C# .NET
• .NET Standard

Version History

Version	Date	Release Notes
1.1.28	2026-Jan-20	NuGet (semver) instead of file version.
1.0.0	2026-Jan-19	Initial release

License

This project is licensed with the MIT license.

Contact

• GitHub Repo
• @goodtocode