Top 20 NuGet assertion Packages

Shouldly - Assertion framework for .NET. The way asserting *Should* be
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.
Simple, fluent, lightweight assertion library to create assertion points in your code.
A collection of xUnit.net assertions, tailored for Tiger libraries. (As source.)
Testify is a unit test assertions, test data creation and contract verification framework. It's not dependent on any specific unit testing framework.
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.
Simple fluent assertions for .NET.
Easy-to-use fluent assertions with actually useful failure messages.
Assertion Error (assertion-error) binding library for Bridge.NET projects.
A minimalistic guard library with Resharper contract annotations
A high-performance, extensible argument validation library.
A collection of xUnit.net assertions, tailored for Tiger libraries.
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 ...
Assert Extensions for the Microsoft Test Framework - MSTest V2
Use code snippet 'assertion' to get the declaration at the top of the file. Then just use Assert.Equal(...) and the like.
Guardly is a defensive programming framework
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.
A class invariants helper library