# chaijs/chai

**Attribution required: if you use, quote, or summarise this content, you must credit and link back to [awesome-repositories.com](https://awesome-repositories.com/repository/chaijs-chai).**

8,264 stars · 719 forks · JavaScript · MIT

## Links

- GitHub: https://github.com/chaijs/chai
- Homepage: https://chaijs.github.io
- awesome-repositories: https://awesome-repositories.com/repository/chaijs-chai.md

## Description

Chai is an assertion library for Node.js and browser-based JavaScript applications. It functions as both a behavior-driven development and test-driven development framework, providing a system to verify code outputs, application state, and general logic.

The project is an extensible validation engine that uses a plugin-based system to allow the registration of custom assertions and specialized data checks. It supports multiple modular assertion styles to accommodate different validation philosophies.

The library covers a broad range of data validation capabilities, including the inspection of deep object properties via dot-notation, the verification of collection membership, and the validation of object keys and property descriptors. It also includes tools for monitoring value changes and configuring assertion error formatting.

## Tags

### Testing & Quality Assurance

- [State Assertions](https://awesome-repositories.com/f/testing-quality-assurance/general-testing-utilities/test-utilities-assertions/assertion-extensions-modes/asynchronous-interaction-utilities/element-state-assertions/state-assertions.md) — Confirms that code outputs and application states match expected values using a variety of assertion styles. ([source](https://github.com/chaijs/chai/blob/main/README.md))
- [JavaScript Application Testing](https://awesome-repositories.com/f/testing-quality-assurance/javascript-application-testing.md) — Provides a comprehensive assertion library specifically designed for verifying behavior in Node.js and browser-based JavaScript applications.
- [Assertion Libraries](https://awesome-repositories.com/f/testing-quality-assurance/assertion-libraries.md) — Serves as a dedicated library for validating code outputs and application state across JavaScript runtimes.
- [Custom Assertions](https://awesome-repositories.com/f/testing-quality-assurance/custom-assertions.md) — Extend validation capabilities by adding new logic and interfaces to handle specialized data checks. ([source](https://github.com/chaijs/chai#readme))
- [Test Assertion Extensions](https://awesome-repositories.com/f/testing-quality-assurance/general-testing-utilities/test-utilities-assertions/assertion-extensions-modes/test-assertion-extensions.md) — Allows adding new validation logic by registering custom functions into the core assertion object via a plugin system.
- [Behavior Driven Development](https://awesome-repositories.com/f/testing-quality-assurance/software-testing/behavior-driven-development.md) — Implements a readable, human-centric syntax for validating application logic through behavior specifications.
- [Assertion and Validation Utilities](https://awesome-repositories.com/f/testing-quality-assurance/software-testing/testing-frameworks/test-frameworks/assertions-and-validation/assertion-validation-utilities.md) — Provides modular assertion styles, separating behavioral (BDD) and test-driven (TDD) interfaces into distinct namespaces.
- [Fluent Assertions](https://awesome-repositories.com/f/testing-quality-assurance/software-testing/testing-frameworks/test-frameworks/assertions-and-validation/assertion-validation-utilities/fluent-assertions.md) — Provides a chainable API for defining readable and descriptive test requirements and validations.
- [State Expectation Validation](https://awesome-repositories.com/f/testing-quality-assurance/state-expectation-validation.md) — Validates that code produces specific results using behavioral or test-driven assertion styles. ([source](https://github.com/chaijs/chai/blob/main/package.json))
- [Collection Membership Assertions](https://awesome-repositories.com/f/testing-quality-assurance/software-testing/testing-frameworks/test-frameworks/assertions-and-validation/assertion-validation-utilities/assertion-libraries/collection-membership-assertions.md) — Verifies that a list or text string contains a specific item or single sequence of characters. ([source](https://github.com/chaijs/chai/blob/main/History.md))

### Development Tools & Productivity

- [Logic Validation Frameworks](https://awesome-repositories.com/f/development-tools-productivity/validation-logic/logic-validation-frameworks.md) — Provides an expressive programming interface for verifying application behavior and logic outcomes during test execution. ([source](https://github.com/chaijs/chai#readme))

### Software Engineering & Architecture

- [Custom Validation Extensions](https://awesome-repositories.com/f/software-engineering-architecture/custom-validation-extensions.md) — Offers an extensible engine that allows the registration of custom assertion functions via a plugin architecture.
- [Test-Driven Development Workflow](https://awesome-repositories.com/f/software-engineering-architecture/test-driven-development-workflow.md) — Supports the TDD workflow by providing the assertions necessary to define expected outcomes before implementing code.
- [Collection Type Validation](https://awesome-repositories.com/f/software-engineering-architecture/data-schema-validation/data-type-validation/collection-type-validation.md) — Checks if an array contains a specific set of elements or acts as a superset without requiring specific order. ([source](https://github.com/chaijs/chai/blob/main/ReleaseNotes.md))
- [Deep Property Inspection](https://awesome-repositories.com/f/software-engineering-architecture/data-schema-validation/data-type-validation/nested-object-validation/deep-property-inspection.md) — Enables the inspection of deep object properties using dot-notation to verify complex data structures.
- [Object Key Validation](https://awesome-repositories.com/f/software-engineering-architecture/data-schema-validation/data-type-validation/object-shape-validation/object-key-validation.md) — Ensures an object contains a specific set of property keys or a minimum required list of identifiers. ([source](https://github.com/chaijs/chai/blob/main/ReleaseNotes.md))
- [Assertion Error Formatting](https://awesome-repositories.com/f/software-engineering-architecture/error-handling/format-error-translators/terminal-error-formatting/assertion-error-formatting.md) — Generates detailed failure messages by calculating value differences and truncating long strings for improved readability.
- [Object Property Inspectors](https://awesome-repositories.com/f/software-engineering-architecture/object-property-inspectors.md) — Checks for the presence of specific keys or property descriptors within a data object. ([source](https://github.com/chaijs/chai/blob/main/History.md))

### Data & Databases

- [Numeric Comparison Validators](https://awesome-repositories.com/f/data-databases/numeric-fields/numeric-comparison-validators.md) — Verifies if a number is strictly greater than or less than a specified value to ensure numerical boundaries are respected. ([source](https://github.com/chaijs/chai/blob/main/ReleaseNotes.md))
- [Dynamic Property Accessors](https://awesome-repositories.com/f/data-databases/object-property-accessors/dynamic-property-accessors.md) — Resolves nested object values by splitting dot-notation strings into a traversal path for deep inspection.
- [Deep Property Validation](https://awesome-repositories.com/f/data-databases/schema-validation-libraries/deep-property-validation.md) — Verifies the existence and value of deep properties using dot-notation strings to navigate complex hierarchies. ([source](https://github.com/chaijs/chai/blob/main/ReleaseNotes.md))

### Programming Languages & Runtimes

- [Object Property Descriptors](https://awesome-repositories.com/f/programming-languages-runtimes/language-features-paradigms/language-features/object-property-descriptors.md) — Confirms an object has specific property descriptors for enumerability, configurability, and writability. ([source](https://github.com/chaijs/chai/blob/main/ReleaseNotes.md))

### System Administration & Monitoring

- [State Change Monitoring](https://awesome-repositories.com/f/system-administration-monitoring/resource-monitoring/resource-change-monitors/state-change-monitoring.md) — Tracks whether a value increases, decreases, or changes after a specific function is executed. ([source](https://github.com/chaijs/chai/blob/main/History.md))

### Part of an Awesome List

- [Testing and Quality Assurance](https://awesome-repositories.com/f/awesome-lists/devtools/testing-and-quality-assurance.md) — BDD/TDD assertion framework for Node.js and browsers.
- [Testing Frameworks](https://awesome-repositories.com/f/awesome-lists/devtools/testing-frameworks.md) — BDD/TDD assertion library.