alexey1312/SnapshotTestingWebP

An extension to SnapshotTesting which allows you to create WebP images

File Size Comparison

Real-world comparison using a complex SwiftUI dashboard (iPhone 13, portrait) with gradients, shadows, cards, and text:

| Format | Size | Reduction | |--------|------|-----------| | PNG | 230 KB | baseline | | WebP Lossless | 53 KB | 77% smaller | | WebP Medium | 49 KB | 79% smaller | | WebP Maximum | 20 KB | 91% smaller |

WebP lossless delivers ~77% savings on typical UI content thanks to optimized compression (libwebp method=2). Lossy WebP consistently delivers 79–91% savings with acceptable visual quality. These results can be verified in the package's test snapshots directory.

Features

WebP Snapshot Testing - Full support for WebP format in snapshot tests
Advanced Compression - Multiple compression quality levels from lossless to maximum compression
Hardware-Accelerated - Optimized encoding with vImage framework (~75-80% faster)
Cross-Platform - iOS 13+, macOS 10.15+, tvOS 13+ support
Drop-in Replacement - Easy migration from PNG snapshots
Complete UI Coverage - UIView, UIViewController, NSView, NSViewController, SwiftUI support
Perceptual Comparison - Hardware-accelerated diffing with Metal Performance Shaders

Installation

Swift Package Manager

Add the following to your Package.swift file:

dependencies: [
    .package(url: "https://github.com/alexey1312/SnapshotTestingWebP.git", from: "1.0.0")
]

Or add it through Xcode: File > Add Packages... and enter the repository URL.

Quick Start

import XCTest
import SnapshotTesting
import SnapshotTestingWebP

class MyViewTests: XCTestCase {
    func testMyView() {
        let view = MyView()

        // WebP snapshot with lossless compression (default)
        assertSnapshot(of: view, as: .imageWebP)

        // WebP with custom compression quality
        assertSnapshot(of: view, as: .imageWebP(compressionQuality: .medium))
    }
}

Compression Quality Options

The library provides several compression quality presets:

| Quality | Raw Value | Description | |---------|-----------|-------------| | .lossless | 1.0 | Perfect quality, larger file size | | .low | 0.8 | 80% quality, good balance | | .medium | 0.5 | 50% quality, recommended for most cases | | .high | 0.2 | 20% quality, smaller files | | .maximum | 0.0 | Smallest file size | | .custom(CGFloat) | 0.0 - 1.0 | Custom quality value |

Usage Examples

// Lossless compression (default) - pixel-perfect accuracy
assertSnapshot(of: view, as: .imageWebP(compressionQuality: .lossless))

// Medium compression - balanced size/quality
assertSnapshot(of: view, as: .imageWebP(compressionQuality: .medium))

// Custom compression level
assertSnapshot(of: view, as: .imageWebP(compressionQuality: .custom(0.75)))

Supported Types

UIKit (iOS/tvOS)

// UIView snapshots
assertSnapshot(of: myView, as: .imageWebP)
assertSnapshot(of: myView, as: .imageWebP(compressionQuality: .medium))

// UIViewController snapshots with device configuration
assertSnapshot(of: myViewController, as: .imageWebP(on: .iPhone13))
assertSnapshot(of: myViewController, as: .imageWebP(on: .iPadPro11))

AppKit (macOS)

// NSView snapshots
assertSnapshot(of: myNSView, as: .imageWebP)

// NSViewController snapshots
assertSnapshot(of: myNSViewController, as: .imageWebP)

SwiftUI

// Size that fits content
assertSnapshot(of: MySwiftUIView(), as: .imageWebP(layout: .sizeThatFits))

// Device-specific layout
assertSnapshot(of: MySwiftUIView(), as: .imageWebP(layout: .device(config: .iPhone13)))

// Fixed size layout
assertSnapshot(of: MySwiftUIView(), as: .imageWebP(layout: .fixed(width: 300, height: 200)))

Advanced Configuration

Precision Control

For lossy compression, you may need to adjust precision thresholds:

assertSnapshot(
    of: view,
    as: .imageWebP(
        precision: 0.98,           // 98% pixel match required
        perceptualPrecision: 0.99, // 99% perceptual precision
        compressionQuality: .medium
    )
)

Scale Configuration

// Custom scale factor
assertSnapshot(
    of: view,
    as: .imageWebP(scale: 2.0, compressionQuality: .lossless)
)

Performance

WebP encoding in this library is highly optimized:

Hardware-accelerated preprocessing using vImage framework
Advanced libwebp configuration with optimized presets
Multi-threaded encoding for improved performance
Smart image scaling with optimal dimension limits

Benchmark Results:

| Metric | Basic libwebp | SnapshotTestingWebP | |--------|---------------|---------------------| | Encoding time (400x300) | ~0.3s | ~0.08s | | Performance improvement | baseline | ~75-80% faster |

Migration from PNG

Replace your existing PNG snapshots with a simple change:

// Before (PNG)
assertSnapshot(of: view, as: .image)

// After (WebP)
assertSnapshot(of: view, as: .imageWebP)

The API is designed to be a drop-in replacement for existing snapshot strategies.

Requirements

iOS 13.0+ / macOS 10.15+ / tvOS 13.0+
Swift 5.2+
Xcode 11.0+

Dependencies

swift-snapshot-testing (1.18.9+)
libwebp (1.4.1+)

License

This library is released under the MIT License. See LICENSE for details.

Contributing

Contributions are welcome! Please feel free to submit a Pull Request.

Package Metadata

Repository: alexey1312/SnapshotTestingWebP

Stars: 2

Forks: 0

Open issues: 0

Default branch: main

Primary language: swift

License: MIT

README: README.md