Top 20 NuGet unit Packages

Interfaces used to configure the TestHelper from other projects
Enumerations tests framework is provided as an NUnit based framework sufficient to exercise the majority of boilerplate issues concerning both Ordinal as well as Bitwise Enumerations.
A library with repository interfaces for using NoSQL
A tiny helper library for creating database integration tests
A framework for implementing testable plugins and code activities for Dynamics CRM 365
Simple full-featured automocking framework
A number of simple methods to test database objects and execute sql. Currently supports Microsoft SQL Server databases.
Algorithms used to persist object state - abstractions
Given a populated object model at runtime, outputs the C# code to recreate the model independently. Able to handle circular references and list initialisations. Particularly useful for snapshotting WPF ViewModels for use in the WPF designer.
CoreDdd unit of work support for Rebus.UnitOfWork package.
A tool designed to facilitate data managment in unit testing. The tool makes JSON data organized in embedded resource easy to access. It provides numberous ways to extract a section of data, and deserialize data.
FakeHttpMessageHandler seamlessly fakes http request sent from System.Net.Http.HttpClient for purpose of unit testing code that previously could only be integration tested.
Breakdance is a testing framework for managing the dangerous dance of shipping public APIs. This package in particular helps generate API reports for OData APIs, and compare them against a prior unit test run. That way, if something in the API surface changed, the unit test will fail.
Easy to use, small, SignalR Core unit testing support with xUnit and Moq. Check my github for NUnit or MSTest version.
Run all of your MSTest assert statements and have each failure message reported summarily.
Fluent helpers to abstract the boiler-plate associated with Unit Testing