# Jest

- **Canonical URI:** https://www.vioscale.ai/software/jest
- **Category:** Testing Tools
- **Vendor:** OpenJS Foundation
- **Homepage:** https://jestjs.io
- **Also known as:** jestjs
- **Profile claimed by vendor:** no
- **Last updated:** 2026-08-05T13:13:53.470Z

## Vioscale score

**78.5 / 100**, confidence 50% (medium).

Composite of weighted, independently-sourced signals (no user reviews, no vendor payment).

| Signal | Score | Weight | Contribution | Evidence present |
|---|--:|--:|--:|:--:|
| price_level | 100 | 0.046 | 4.6 | ✓ |
| reliability | 0 | 0.062 | 0 | - |
| capabilities | 74.7 | 0.123 | 9.2 | ✓ |
| github_stars | 87.9 | 0.038 | 3.3 | ✓ |
| integrations | 0 | 0.062 | 0 | - |
| github_activity | 52.3 | 0.138 | 7.2 | ✓ |
| release_cadence | 96.7 | 0.077 | 7.4 | ✓ |
| security_posture | 0 | 0.1 | 0 | - |
| package_downloads | 99.6 | 0.2 | 19.9 | ✓ |
| pricing_transparency | 25 | 0.062 | 1.6 | ✓ |
| stackoverflow_activity | 82.9 | 0.092 | 7.6 | ✓ |

## Pricing

_As of 2026-08-05, [verify at source](https://jestjs.io). Independently observed._

Open source · Free tier

## About

A JavaScript testing framework designed to ensure correctness of any JavaScript codebase. Works with Babel, TypeScript, Node, React, Angular, Vue and more.

_Independently observed._

## Platform & deployment

- **Platforms:** CLI

## Capabilities

_The capabilities that matter for Testing Tools. "-" = undocumented, not absent._

| Capability | Supported |
|---|:--:|
| **Core** | |
| Test types | - |
| Browser automation | - |
| Built-in assertion library | ✓ |
| **Isolation** | |
| Mocking / stubbing | ✓ |
| **Techniques** | |
| Snapshot testing | ✓ |
| **Performance** | |
| Parallel execution | ✓ |
| **Insight** | |
| Code coverage | ✓ |
| **DX** | |
| Watch mode | - |
| **Ops** | |
| CI integration | - |
| **Core** | |
| Languages | JavaScript, TypeScript |

## FAQ

### What is Jest and who should use it?

Jest is a testing framework for JavaScript projects that provides tools for writing and running unit tests. It is designed for developers building applications with JavaScript, TypeScript, React, Angular, Vue, and Node.js, and emphasizes minimal configuration while offering extensive built-in testing capabilities.

_Source: [https://jestjs.io](https://jestjs.io)._

### Is Jest open-source and free to use?

Yes, Jest is open-source and free to use under an open-source license, maintained by the OpenJS Foundation and its community contributors. There is no commercial licensing model, paid tier, or associated costs for using Jest.

_Source: [https://jestjs.io](https://jestjs.io)._

### How do I install and get started with Jest?

Jest can be installed as a development dependency using npm, yarn, pnpm, or bun by running a single install command. After installation, you add a test script to your package.json, create test files alongside your source code, and run tests immediately with minimal or no configuration required.

_Source: [https://jestjs.io/docs/getting-started](https://jestjs.io/docs/getting-started)._

### What does Jest's snapshot testing feature do?

Snapshot testing captures the output of a component or function and stores it in a reference file, then compares future test runs against that snapshot to detect unintended changes. This is particularly useful for testing React components, API responses, and other complex serialized values where checking exact output structure is important.

_Source: [https://jestjs.io/docs/snapshot-testing](https://jestjs.io/docs/snapshot-testing)._

### What are mock functions in Jest and why use them?

Mock functions let you replace real function implementations with test versions that capture how they were called, what arguments they received, and what they returned. This enables isolation testing and verification of interactions between code units without depending on external implementations.

_Source: [https://jestjs.io/docs/mock-functions](https://jestjs.io/docs/mock-functions)._

### Does Jest provide built-in code coverage reporting?

Yes, Jest includes built-in code coverage reporting that can be enabled with the --coverage flag, which generates coverage reports without requiring additional setup or external tools. You can configure coverage collection to target specific files, specify coverage thresholds, and choose between different coverage providers.

_Source: [https://jestjs.io/docs/cli](https://jestjs.io/docs/cli)._

### Can Jest work with TypeScript and other JavaScript frameworks?

Jest supports TypeScript through ts-jest or Babel setup, and integrates with popular frameworks including React, Angular, Vue, and Node.js. The framework is flexible and extensible, allowing configuration for different transpilers and module systems including webpack and CommonJS environments.

_Source: [https://jestjs.io/docs/getting-started](https://jestjs.io/docs/getting-started)._

### What are Jest's core strengths as a testing framework?

Jest emphasizes zero-configuration setup, parallel test execution for speed, built-in snapshot testing, comprehensive mocking and assertion APIs, clear error messages, and code coverage out-of-the-box. These features make it production-ready without requiring a complex learning curve or setup for typical JavaScript projects.

_Source: [https://jestjs.io](https://jestjs.io)._


## Facts

Every value below carries its source and our confidence. Facts are re-crawled on a freshness schedule.

### adoption

| Attribute | Value | Source | Retrieved | Confidence |
|---|---|---|---|---|
| adoption.package_downloads_weekly | 46,603,807 | [link](https://www.npmjs.com/package/jest) | 2026-07-31 | 85% (high) |
| adoption.github_stars | 45,454 | [link](https://github.com/jestjs/jest) | 2026-07-31 | 90% (high) |
| adoption.stackoverflow_questions | 44,000 | [link](https://stackoverflow.com/questions/tagged/jestjs) | 2026-07-30 | 75% (high) |

### activity

| Attribute | Value | Source | Retrieved | Confidence |
|---|---|---|---|---|
| activity.commits_last_30d | 45 | [link](https://github.com/jestjs/jest/pulse) | 2026-07-30 | 65% (medium) |

### release

| Attribute | Value | Source | Retrieved | Confidence |
|---|---|---|---|---|
| release.cadence_days | 6 | [link](https://github.com/jestjs/jest/releases) | 2026-07-31 | 70% (medium) |

### license

| Attribute | Value | Source | Retrieved | Confidence |
|---|---|---|---|---|
| license.spdx | MIT | [link](https://github.com/jestjs/jest) | 2026-07-31 | 99% (high) |

### pricing

| Attribute | Value | Source | Retrieved | Confidence |
|---|---|---|---|---|
| pricing.model | commercial | [link](https://jestjs.io) | 2026-08-05 | 60% (medium) |
| pricing.free_tier | yes | [link](https://jestjs.io) | 2026-08-05 | 60% (medium) |
| pricing.price_level | free | [link](https://jestjs.io) | 2026-08-05 | 60% (medium) |

### language

| Attribute | Value | Source | Retrieved | Confidence |
|---|---|---|---|---|
| language.primary | TypeScript | [link](https://github.com/jestjs/jest) | 2026-07-31 | 90% (high) |

### market

| Attribute | Value | Source | Retrieved | Confidence |
|---|---|---|---|---|
| market.availability | `{"source":"https://jestjs.io","hqCountry":"US","confidence":0.95,"primaryMarkets":["US"],"availabilityScope":"global","availableCountries":[],"notAvailableCountries":[]}` | [link](https://jestjs.io) | 2026-07-30 | 95% (high) |

### content

| Attribute | Value | Source | Retrieved | Confidence |
|---|---|---|---|---|
| content.faq | `[{"answer":"Jest is a testing framework for JavaScript projects that provides tools for writing and running unit tests. It is designed for developers building applications with JavaScript, TypeScript, React, Angular, Vue, and Node.js, and emphasizes minimal configuration while offering extensive built-in testing capabilities.","source":"https://jestjs.io","question":"What is Jest and who should use it?","confidence":0.95},{"answer":"Yes, Jest is open-source and free to use under an open-source license, maintained by the OpenJS Foundation and its community contributors. There is no commercial licensing model, paid tier, or associated costs for using Jest.","source":"https://jestjs.io","question":"Is Jest open-source and free to use?","confidence":0.95},{"answer":"Jest can be installed as a development dependency using npm, yarn, pnpm, or bun by running a single install command. After installation, you add a test script to your package.json, create test files alongside your source code, and run tests immediately with minimal or no configuration required.","source":"https://jestjs.io/docs/getting-started","question":"How do I install and get started with Jest?","confidence":0.95},{"answer":"Snapshot testing captures the output of a component or function and stores it in a reference file, then compares future test runs against that snapshot to detect unintended changes. This is particularly useful for testing React components, API responses, and other complex serialized values where checking exact output structure is important.","source":"https://jestjs.io/docs/snapshot-testing","question":"What does Jest's snapshot testing feature do?","confidence":0.95},{"answer":"Mock functions let you replace real function implementations with test versions that capture how they were called, what arguments they received, and what they returned. This enables isolation testing and verification of interactions between code units without depending on external implementations.","source":"https://jestjs.io/docs/mock-functions","question":"What are mock functions in Jest and why use them?","confidence":0.95},{"answer":"Yes, Jest includes built-in code coverage reporting that can be enabled with the --coverage flag, which generates coverage reports without requiring additional setup or external tools. You can configure coverage collection to target specific files, specify coverage thresholds, and choose between different coverage providers.","source":"https://jestjs.io/docs/cli","question":"Does Jest provide built-in code coverage reporting?","confidence":0.92},{"answer":"Jest supports TypeScript through ts-jest or Babel setup, and integrates with popular frameworks including React, Angular, Vue, and Node.js. The framework is flexible and extensible, allowing configuration for different transpilers and module systems including webpack and CommonJS environments.","source":"https://jestjs.io/docs/getting-started","question":"Can Jest work with TypeScript and other JavaScript frameworks?","confidence":0.93},{"answer":"Jest emphasizes zero-configuration setup, parallel test execution for speed, built-in snapshot testing, comprehensive mocking and assertion APIs, clear error messages, and code coverage out-of-the-box. These features make it production-ready without requiring a complex learning curve or setup for typical JavaScript projects.","source":"https://jestjs.io","question":"What are Jest's core strengths as a testing framework?","confidence":0.9}]` | [link](https://jestjs.io) | 2026-07-30 | 94% (high) |

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*Source: Vioscale (https://www.vioscale.ai/software/jest). Independent, evidence-based software intelligence. Cite the canonical URI.*