americanexpress/jest-image-snapshot
Jest Image Snapshot
jest-image-snapshot is a Node.js image testing library and visual comparison engine designed for visual regression testing within Jest. It provides a custom matcher to compare current images against baseline snapshots to identify pixel differences.
The tool generates image diffs that highlight specific divergences between baseline and received snapshots. It includes mechanisms to update baseline images when changes are approved and allows for sensitivity tuning via pixel count, percentage thresholds, or blur to ignore noise.
The library covers image snapshot management, including custom storage configuration for directory paths and utilities to identify and remove obsolete snapshots no longer associated with active tests. It supports both pixel-by-pixel and structural similarity algorithms for verifying user interface consistency.
Features
- Visual Regression Testing - Automates the capture and comparison of screenshots to detect unintended UI changes within Jest.
- Difference Map Generation - Produces visual images that highlight the specific pixel-level differences between baseline and received snapshots.
- Node.js Image Processing - Provides a Node.js library for automating UI consistency verification via pixel-by-pixel analysis.
- Baseline Image Storage - Persists approved reference images in a directory structure to serve as the source of truth for regressions.
- Visual Consistency Testing - Ensures consistent visual layouts across different versions of a web application through automated image comparisons.
- Pixel-Level Image Comparison - Compares image buffers at the pixel level to identify visual changes based on color variance.
- Visual Snapshot Comparisons - Executes visual screenshot-based comparisons to verify UI correctness programmatically.
- Frontend Visual QA - Verifies that styling and layout changes do not break the visual appearance of frontend interfaces.
- Custom Matchers - Provides a custom matcher for comparing current images against baseline snapshots to identify differences.
- Visual Difference Maps - Generates images that highlight pixel-level discrepancies between a current screenshot and a reference baseline.
- Obsolete Image Identification - Tracks image files no longer associated with active tests to maintain clean storage.
- Snapshot Archive Deletions - Identifies and deletes baseline images no longer associated with active tests to free disk space.
- Visual Snapshot Lifecycles - Tracks and purges baseline images that are no longer associated with active test suites.
- Visual Snapshot Management - Handles the lifecycle of reference images by updating baselines and removing obsolete snapshots.
- Comparison Tuning - Provides interfaces for adjusting mismatch thresholds and applying blur to ignore visual noise.
- Difference Thresholds - Determines test failure by calculating if the number of differing pixels exceeds a specified threshold.
- Baseline Image Updates - Allows replacing existing reference snapshots with new images when visual changes are approved.
- Pixel-Matching Analysis - Configures the pixel-matching mechanism and structural similarity thresholds for image comparison.
- Snapshot Testing Utilities - Visual regression testing via image buffer snapshots
- Testing Frameworks - Jest matcher for performing image comparisons using pixelmatch.
Star history
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