Top 3 C# Assertion Projects

Fluent Assertions

7 3,593 9.5 C#

A very extensive set of extension methods that allow you to more naturally specify the expected outcome of a TDD or BDD-style unit tests. Targets .NET Framework 4.7, as well as .NET Core 2.1, .NET Core 3.0, .NET 6, .NET Standard 2.0 and 2.1. Supports the unit test frameworks MSTest2, NUnit3, XUnit2, MSpec, and NSpec3.
AutoFixture

11 3,219 4.9 C#

AutoFixture is an open source library for .NET designed to minimize the 'Arrange' phase of your unit tests in order to maximize maintainability. Its primary goal is to allow developers to focus on what is being tested rather than how to setup the test scenario, by making it easier to create object graphs containing test data.

Project mention: API: Go, .NET, Rust | /r/dotnet | 2023-12-09

Yes, it does feel like some of the "standard stuff" in other more nuanced languages are missing (especially miss AutoFixture ngl). Some of those are a conscious decison by the golang team for example.

WorkOS

workos.com sponsored

The modern identity platform for B2B SaaS. The APIs are flexible and easy-to-use, supporting authentication, user identity, and complex enterprise features like SSO and SCIM provisioning.
fluentassertions.analyzers

1 128 8.9 C#

Analyzers based on the FluentAssertions best practices docs

Project mention: Optimizing C# code analysis for quicker .NET compilation | dev.to | 2023-11-14

Several well-known NuGet packages such as xUnit.net, FluentAssertions, StyleCop, Entity Framework Core, and others include by default a significant number of Roslyn analyzers. They help you adhere to the conventions and best practices of these libraries.

NOTE: The open source projects on this list are ordered by number of github stars. The number of mentions indicates repo mentiontions in the last 12 Months or since we started tracking (Dec 2020).