Open-source alternatives to Assert

Arktype is a TypeScript runtime validation library and schema orchestrator. It synchronizes TypeScript types with runtime data validation, allowing users to define type-safe schemas that ensure unknown data adheres to specific structures during application execution. The project distinguishes itself by using set-theory type analysis to determine intersections and subtype compatibility, alongside JIT-compiled validation functions for optimized performance. It supports advanced type modeling through branded type constraints, recursive alias resolution, and the ability to generate runtime valida

TUnit is a comprehensive C# testing framework, mocking library, and fluent assertion tool. It utilizes source generation for test discovery and mock creation, ensuring compatibility with Native AOT and IL trimming by eliminating the need for runtime reflection and proxies. The framework provides specialized capabilities for integration testing, including the management of distributed application lifecycles, isolated database schemas, and the correlation of telemetry and logs across process boundaries via OTLP. It also includes an HTTP testing utility to intercept network exchanges and mock AP

AWS Powertools for Python is a utility framework designed for building production-ready Python functions on AWS Lambda. It provides a comprehensive suite of tools for observability, event parsing, routing, and idempotency management to streamline the development of serverless applications. The project distinguishes itself through specialized capabilities for event-driven architectures and AI agent orchestration. It enables the implementation of AI agents by exposing functions as tools via OpenAPI schemas and managing conversation states. Additionally, it features an idempotency library that p

TypeBox is a JSON schema generator and TypeScript data validator. It functions as a type builder that creates compliant JSON schema definitions while providing a mechanism for synchronizing runtime validation logic with compile-time types. The project allows for the automatic derivation of static TypeScript interfaces from schema definitions to eliminate redundant type declarations. It converts complex type constructs into schema fragments and resolves static types to maintain consistency between data shapes and code. The system covers runtime type checking and data validation through the us

Yup is a JavaScript schema validation library used to define data shapes and validate runtime values. It functions as an object schema validator and a data coercion engine, allowing developers to transform raw input values into desired types before performing validation checks. The library is distinguished by its support for dynamic schema validation, where rules can be adjusted at runtime based on sibling field values or external context. It also enables recursive data structuring for polymorphic fields and provides a system for extracting static TypeScript interfaces from runtime schema def

class-validator is a TypeScript class validation library that uses decorators to define constraints and rules for object properties. It functions as a decorator-based schema validator that ensures data integrity and structural correctness through a combination of synchronous checks and promise-based asynchronous rules. The library provides a recursive validation system for checking complex data hierarchies, including nested classes and individual elements within collections. It includes an object property whitelist utility capable of stripping undocumented properties or blocking unknown field

This project is a protocol buffer validation plugin and code generator that creates consistent validation logic across multiple programming languages. It functions as a compiler extension for the Protocol Buffer toolchain, allowing developers to define semantic constraints directly within schema files to ensure data consistency. The tool uses custom options to embed validation rules into message definitions, mapping these schema constraints to language-specific implementation patterns. It employs predicate-based constraint checking and recursive traversal to enforce rules across nested messag

Go Package of validators and sanitizers for strings, numerics, slices and structs

Tape is a TAP-producing test framework for Node.js that provides assertions, spies, subtests, and isolated test harnesses. It functions as both a test runner and an assertion library, outputting results in the Test Anything Protocol format for machine or human consumption. The framework manages test execution through callback-based async control, plan-based auto termination, and subtest stack isolation. It includes a spy wrapper system that replaces object methods with call-recording wrappers that restore originals during teardown, along with a teardown callback registry that collects and exe

Cog is a machine learning packaging tool and containerized model wrapper that bundles models and their dependencies into standardized Docker containers. It functions as an environment manager and inference server, ensuring consistent model execution across different hardware systems by resolving GPU drivers, system libraries, and Python dependencies. The project distinguishes itself by automatically generating RESTful HTTP servers and OpenAPI schemas based on defined model input and output types. It manages large model weights as external fixtures to optimize image size and utilizes a slot-ba

pysheeet is a technical reference library providing a curated collection of code snippets and implementation patterns for advanced Python development, system integration, and high-performance computing. It serves as a comprehensive guide for implementing low-level network programming, native C extensions, and asynchronous and concurrent programming. The project provides specialized frameworks for the development and deployment of large language models, including tools for distributed GPU inference and high-performance serving. It also includes detailed patterns for high-performance computing

Superstruct is a JavaScript and TypeScript data validation library used to verify that data structures match defined shapes and types. It functions as a composable schema builder and a TypeScript schema validator, ensuring that runtime data checks remain synchronized with static type definitions. The library features a data coercion engine that transforms input values or injects default values before the validation process is executed. It enables the creation of complex validation rules by nesting, merging, or omitting properties from existing structures. Its capabilities cover the validatio

Hug is a type-driven Python web framework designed for building APIs. It uses Python type annotations to automatically validate and convert incoming request data and to format outgoing responses. The framework functions as an automated documentation tool by extracting function signatures and markers from source code to generate accessible API specifications. It also supports non-blocking coroutines for asynchronous API processing to handle background tasks without interrupting the main request cycle. The project provides capabilities for REST API development, including route mapping, endpoin

FluentValidation is a strongly-typed data validation library for .NET. It functions as a rule engine and input validation framework used to define and execute complex business rules and constraints for data objects. The library utilizes a fluent interface API, allowing the construction of readable and declarative validation constraints through method chaining. It leverages generics and lambda expressions to enforce data integrity and business logic at compile time. The project covers the enforcement of business rules, strongly-typed data validation, and input sanitization workflows to verify

APIStar is an OpenAPI framework providing a toolkit for building and verifying web APIs. It functions as an API schema validator, a traffic auditor, and a documentation generator to ensure compliance with API specifications and data types. The project converts OpenAPI and Swagger schemas into visual developer guides using customizable themes. It also implements a dynamic API client that adapts to defined schemas to send requests to remote servers. The framework includes capabilities for validating API schemas to identify structural mistakes and auditing incoming and outgoing web traffic agai

Lodash is a JavaScript utility library and data manipulation toolkit. It provides a collection of modular functions for transforming, filtering, and validating arrays, objects, strings, and numbers. The project functions as a functional programming toolkit, offering capabilities for function composition, currying, and lazy evaluation. It includes mechanisms for execution control, such as debouncing and throttling, to manage the timing and frequency of function invocations. The library covers a broad surface of data operations, including deep cloning and merging of complex nested structures,

This project is a Git commit standardization tool and semantic commit generator. It serves as an assistant to align code changes with semantic versioning by enforcing a consistent commit structure and formatting rules. The utility uses interactive prompts to gather user input, which it then validates against semantic categories and interpolates into predefined templates. This process automates the generation of standardized messages, ensuring that each commit follows a specific format to improve project history and traceability. The system also handles commit metadata structuring, including

Respect/Validation is a PHP validation library that operates on single input values through a fluent, chainable rule system. Each validator instance builds a linear constraint pipeline by appending rules to an internal stack, executing them sequentially and short-circuiting on the first failure. The library captures validation failures as structured exceptions, enabling callers to inspect detailed error metadata programmatically and respond with meaningful messages. The library distinguishes itself through its exception-based error handling model, which provides programmatic access to validat

Pydantic is a data validation library and parsing framework for Python. It functions as a type-based schema validator that uses standard Python type annotations to ensure input data conforms to predefined structural schemas. The project provides capabilities for parsing raw data into typed objects through automatic type conversion and validation. This includes the serialization of data and the validation of data structures to enforce correctness. The framework covers several application areas, including the verification of API requests and the management of application configurations. It all

This project is the JavaScript reference implementation of the GraphQL specification. It provides a query engine and schema parser designed to parse, validate, and execute queries to retrieve or mutate data based on a defined schema. The implementation includes a framework for mapping codebase structures to a strongly typed system and a tool for converting query strings into abstract syntax trees for programmatic analysis. The library covers the full surface of GraphQL API implementation, including schema definition, language parsing, and query validation. It provides the necessary infrastru

prop-types is a JavaScript object validator and runtime type checker. It serves as a development tool for verifying that object properties match predefined specifications, primarily used to ensure that data passed into React components aligns with expected types. The utility detects data inconsistencies by logging warnings to the console when mismatches occur, rather than throwing exceptions. It employs a stateful warning cache to prevent duplicate logs and restricts validation logic to non-production environments to avoid performance overhead in released builds. The project covers data vali

Pkl is a configuration-as-code language used to define, validate, and generate structured configuration files. It functions as a type-safe configuration generator that enforces data integrity through a strongly-typed schema, ensuring configuration values meet defined constraints and types during evaluation. The project distinguishes itself by acting as both a configuration file generator and a binding generator. It transforms high-level programmable definitions into static formats such as JSON, YAML, or XML, and produces language-specific source code to synchronize settings and provide type s

System Designer is a visual modeling environment for constructing software architectures, data schemas, and component behaviors. It functions as a low-code platform that allows users to define complex systems through a drag-and-drop interface, representing components and their relationships as interconnected nodes and edges. The platform distinguishes itself by providing a live runtime environment where defined models can be executed and inspected in real-time. It performs dynamic type validation on system operations to ensure consistency and allows for the modular composition of applications

Joi is a JavaScript data validation library used to define schemas that validate, cast, and sanitize data objects. It functions as an object schema validator and parser, ensuring that input data matches specific types and formats before it is processed by an application. The library features a conditional validation engine capable of dynamic schema enforcement, where validation logic and dependencies change based on the values of other keys within an object. It also serves as a data casting and sanitization tool, transforming input values into target types and removing sensitive keys from the

v8n is a JavaScript data validation library used to verify that values, objects, and arrays meet specific criteria. It functions as a schema-based validator and an asynchronous validation engine, utilizing a fluent API to construct sequences of chainable rules and constraints. The framework is distinguished by its ability to execute promises and network requests during the validation process to determine if a value is valid. It allows for the creation of reusable validation schemas and provides a customizable rule framework where users can define their own logic and configure how error result

Underscore is a JavaScript utility library providing a suite of functional programming and data manipulation helpers. It serves as a framework for transforming data collections, composing functions, managing objects, and performing precise data type validation without modifying core language prototypes. The project includes a functional programming toolkit designed to control function execution timing and behavior through techniques such as debouncing, throttling, and partial application. It also provides a dedicated object manipulation utility for cloning, merging, picking, and omitting prop

This library is a PHP framework designed for validating and sanitizing incoming data. It provides a structured approach to ensuring that information conforms to expected formats and integrity requirements before it is processed or stored by an application. The project utilizes a fluent interface to construct validation logic, allowing for the definition of complex rules through chainable methods. It employs a strategy-based execution model where individual validation components are encapsulated and can be dynamically assigned to data fields. When validation fails, the system uses an exception