# fluentassertions/fluentassertions

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.

Repository: https://github.com/fluentassertions/fluentassertions
Canonical: https://ross.abutalabs.com/products/fluentassertions
Homepage: https://xceed.com/products/unit-testing/fluent-assertions/
Language: C#
License: NOASSERTION
License Family: other
Topics: fluent-assertions, c-sharp, assertions, tdd, bdd-style, unit-testing, xunit, mstest, hacktoberfest
Last push: 2026-08-25T12:36:46+00:00

## Health v2 (maintenance only)
Score: 94/100 (v2, computed 2026-09-02T17:46:02.011165+00:00)
- activity 99, release rhythm 83, longevity 100
- inputs: {"age_days": 4784, "days_push": 8, "days_rel": 113, "gap_med": 26.5, "n_releases_24m": 21}
- flags: no_license
- formula: round(0.45*activity + 0.35*rhythm + 0.20*longevity); archived -> min(score, 10)

## Adoption (not part of the score)
Stars 3816, forks 724 (observed 2026-08-28T04:08:20.906859+00:00)

## What it is
Fluent Assertions is a .NET library providing an extensive set of extension methods for writing readable, fluent assertions in TDD and BDD-style unit tests. It supports multiple .NET platforms and integrates with test frameworks such as MSTest, NUnit, XUnit, MSpec, and NSpec.

## Use cases
- write readable unit test assertions in .NET
- fluently assert collection contents in C# tests
- verify exceptions are thrown with specific messages
- chain assertions on object graphs
- improve TDD/BDD test readability

## When to choose
- you write .NET unit tests and want expressive, chainable assertions
- you use MSTest, NUnit, XUnit, MSpec, or NSpec and want better failure messages
- you follow TDD or BDD practices in C#

## When to avoid
- you are not developing on .NET
- you need a permissively licensed library without commercial subscription requirements
- you prefer plain built-in framework assertions

## Facets
- artifact type: library
- maturity: active
- function: testing
- domain: testing, developer-tools
- platform: dotnet, cross-platform
- tags: assertions, tdd, bdd, unit-testing, xunit, nunit, mstest, fluent-api, c-sharp

## Member repositories
- fluentassertions/fluentassertions (main) score 94

## Provenance
- Observed fields: from GitHub, fetched 2026-08-28T04:08:20.906859+00:00.
- Health v2: computed from the inputs above; adoption is never an input.
- Inferred fields (summary, facets, guidance): AI-extracted, prompt v1, taxonomy v1, on 2026-08-29T18:26:32.653661+00:00, confidence not recorded.
  - readme: https://github.com/fluentassertions/fluentassertions (fetched 2026-08-28T04:08:20.906859+00:00, sha 24de61325bf5)
  - homepage: https://xceed.com/products/unit-testing/fluent-assertions/ (fetched 2026-08-29T09:21:28.744135+00:00, sha 4652364aa8b6)
  - site_page: https://xceed.com/about-us (fetched 2026-08-29T09:21:28.753530+00:00, sha 033a2aa84402)
  - site_page: https://xceed.com/documentation (fetched 2026-08-29T09:21:28.757731+00:00, sha c142e1837db0)
  - site_page: https://xceed.com/documentation/xceed-fluent-assertions-for-net/index.html (fetched 2026-08-29T09:21:28.759421+00:00, sha cd2dc3eb05f4)
  - site_page: https://xceed.com/pricing (fetched 2026-08-29T09:21:28.755949+00:00, sha 36434f351d40)
- Data as of 2026-08-30T08:39:29.467469+00:00.