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swift-snapshot-testing skill

/swift-snapshot-testing

This skill helps Swift developers adopt robust snapshot testing with views, images, and custom formats across XCTest and Swift testing workflows.

npx playbooks add skill nonameplum/agent-skills --skill swift-snapshot-testing

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SKILL.md
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---
name: swift-snapshot-testing
description: A library for snapshot testing in Swift with support for views, images, and custom formats
---

# SnapshotTesting

Powerfully flexible snapshot testing.

## Documentation Structure

### Essentials

- **Integrating with test frameworks** ([Articles/IntegratingWithTestFrameworks.md](Articles/IntegratingWithTestFrameworks.md)): Learn how to use snapshot testing in the two main testing frameworks: Xcode's XCTest and Swift's
- **Migration guides** ([Articles/MigrationGuides/MigrationGuides.md](Articles/MigrationGuides/MigrationGuides.md)): Learn how to upgrade your application to the newest version of this library.

### Strategies

- **Defining custom snapshot strategies** ([Articles/CustomStrategies.md](Articles/CustomStrategies.md)): While SnapshotTesting comes with a wide variety of snapshot strategies, it can also be extended with

### Configuration


### Deprecations

- **Deprecations** ([Extensions/Deprecations/SnapshotTestingDeprecations.md](Extensions/Deprecations/SnapshotTestingDeprecations.md))

## Usage Notes

- Documentation is organized progressively from getting started to advanced topics
- Start with the Introduction or Getting Started section
- Consult specific guides for detailed information

## License & Attribution

This skill contains content converted from DocC documentation format.

Overview

This skill presents Swift SnapshotTesting, a library for snapshot testing Swift code with support for views, images, and custom formats. It guides users from integration with testing frameworks through migration and advanced customization. The documentation is organized progressively to take developers from getting started to defining custom snapshot strategies.

How this skill works

The skill explains how to capture and compare snapshots of UI views, images, and other serializable outputs across test runs. It shows integration points for XCTest and other frameworks, how to store reference snapshots, and how to write custom snapshot strategies and formats. It also covers migration steps and deprecation notes to keep tests stable across library updates.

When to use it

  • Validate UI rendering across changes to catch regressions early
  • Test image outputs and visual components that are hard to assert with unit tests
  • Ensure consistent serialization for complex model or view states
  • Integrate snapshot checks into CI to prevent visual regressions
  • Extend default behavior with custom snapshot formats or strategies

Best practices

  • Start with small, focused snapshots (single view or component) to simplify diffs
  • Store reference snapshots under version control and review snapshot updates carefully
  • Use device/environment-specific strategies to avoid flakiness from platform differences
  • Write tests that assert intent; update snapshots only when a deliberate visual change occurs
  • Leverage migration guides and deprecation notes when upgrading the library to avoid test breakage

Example use cases

  • Capture a UITableView or SwiftUI View snapshot to detect layout regressions
  • Compare generated chart images across data changes to ensure rendering consistency
  • Create a custom snapshot strategy to serialize and compare a complex model object
  • Integrate snapshot tests into CI so failed visual diffs block merges until reviewed

FAQ

How do I get started with XCTest?

Add the library to your test target, import it in your test files, and use the provided assertSnapshot helpers to record and compare snapshots within XCTest tests.

Can I create custom snapshot formats?

Yes. The skill explains how to define custom snapshot strategies and formats so you can serialize and compare nonstandard outputs or apply specialized diffing logic.