Assertions Python Packages

pandera

A light-weight, flexible, and expressive statistical data testing library

asserts

Stand-alone Assertions for Python

grappa

Behavior-oriented, expressive, human-friendly Python assertion library for the 21st century

assertpy2

Fluent, fully typed assertion library for Python: your type checker sees only the assertions that fit the value, and every failure carries a structured diff. Soft assertions, polling, inline snapshots, OpenAPI contracts.

aiexpect

Assertions for non-deterministic AI text. Drop into pytest, get a Trust Score + HTML report. Free-first: rules, local embeddings, then your own LLM judge.

assertionlib

A package for performing assertions and providing informative exception messages.

mcp-assert

The testing standard for MCP servers. Lint (14 rules), test, and fuzz over real stdio/SSE/HTTP transport. 18 assertion types in YAML. Found 4,794 schema issues across 55 servers. Any language, no mocks, single binary.

fluentcheck

Fluent assertions for Python

sentienceapi

A verification-first runtime for AI web agents — with Jest-style assertions and token-efficient snapshots

behave-kit

The Swiss-army knife for Behave — soft assertions, typed context, conditional skip, environment management, tag-based fixtures, data loading, context dump, and step suggestions. Adopt incrementally with 3 levels of integration.

hwcontract

Judge hardware timing, serial boot logs and decoded traces against YAML contracts. pass/marginal/fail with evidence. MCP server, pytest plugin, GitHub Action.

pytest-mcp-assert

The testing standard for MCP servers. Lint (14 rules), test, and fuzz over real stdio/SSE/HTTP transport. 18 assertion types in YAML. Found 4,794 schema issues across 55 servers. Any language, no mocks, single binary.

pyssertive

Fluent, chainable assertions for Django tests. Inspired by Laravel's elegant testing API.

lovely-assertions

Fluent, strictly-typed assertions for Python tests: typed discoverability, real narrowing, and failure messages that explain themselves.

business-use-core

Track, validate, and visualize business flows in production applications.

selenium-expect

Fluent expect() assertions with auto-retry for Selenium Python. 150+ assertions, soft assertions, custom matchers, locator-based expects, configurable polling with backoff. Zero dependencies beyond Selenium 4.10+.

pytest-llm-assert

Natural language assertions for pytest using LLMs

business-use

Track, validate, and visualize business flows in production applications.

rendercheck

Assertions for AI-generated media. The worst bugs in generated video and audio don't throw — pace, loudness, truncation, dead air, wrong presenter, broken layout. rendercheck makes them throw.

grappa-http

HTTP assertion plugin for grappa

conditions-py

Conditions libary for Python 3+

sparquet-cola

Data quality for Spark that runs where your data already is. SODA-style metric checks, SQL rules, schema contracts — plus a valid/invalid split that tells you which rule rejected each row. Pure PySpark, no extra services.

sentience-python

A verification-first runtime for AI web agents — with Jest-style assertions and token-efficient snapshots

predicate-sdk

A verification-first runtime for AI web agents — with Jest-style assertions and token-efficient snapshots