Top 20 NuGet assertion Packages

Shouldly - Assertion framework for .NET. The way asserting *Should* be
Simple fluent assertions for .NET.
Assertion Error (assertion-error) binding library for Bridge.NET projects.
CodeJam is a set of handy reusable .NET components that can simplify your daily work and save your time when you copy and paste your favorite helper methods and classes from one project to another.
A collection of xUnit.net assertions, tailored for Tiger libraries.
A collection of xUnit.net assertions, tailored for Tiger libraries. (As source.)
A simple diff comparison asserter that makes it easy to assert if two texts (strings) are equal, and display the differences in a diff tool if they are not. Simply put it is a much simpler (and dumber) version of ApprovalTests that should get the job done for simple scenarios. You can easily create ...
Testify is a unit test assertions, test data creation and contract verification framework. It's not dependent on any specific unit testing framework.
Simple, fluent, lightweight assertion library to create assertion points in your code.
Testify is a unit test assertions, test data creation and contract verification framework. It's not dependent on any specific unit testing framework. Testify.Moq adds mocking support via Moq.
A high-performance, extensible argument validation library.
Assert Extensions for the Microsoft Test Framework - MSTest V2
Easy-to-use fluent assertions with actually useful failure messages.
Use code snippet 'assertion' to get the declaration at the top of the file. Then just use Assert.Equal(...) and the like.
Little helper on assertion.
Guardly is a defensive programming framework
A minimalistic guard library with Resharper contract annotations
Test Run Extensions for the Microsoft Test Framework - MSTest V2
A JavaScript library with function argument assertions, a function parser and assertion wrapper functionality. By wrapping your functions you get defined, notNull, bool, func, number, object, string and notEmpty assertions for free. The interface is specially optimised for the Visual Studio JavaScri...
A fluent assertion module for PowerShell. Part of the PSST PowerShell Suite for Testing.