fluentassertions

Overview

Per fluentassertions.com:

FluentAssertions is the de facto fluent-assertion library for .NET. Works with any of xunit-tests, nunit-tests, mstest-tests.

Important license change note: from v8, "commercial use requires a paid license", while v8+ stays "free for open-source projects and non-commercial use"; v7 "will remain fully open-source indefinitely" (per fluentassertions.com/releases). Commercial projects either buy a v8+ license or pin to v7; open-source and non-commercial projects can use v8+ free.