https://github.com/eventbrite/swift-snapshot-testing
📸 Delightful Swift snapshot testing.
https://github.com/eventbrite/swift-snapshot-testing
Last synced: 3 months ago
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📸 Delightful Swift snapshot testing.
- Host: GitHub
- URL: https://github.com/eventbrite/swift-snapshot-testing
- Owner: eventbrite
- License: mit
- Created: 2022-08-26T16:33:43.000Z (almost 3 years ago)
- Default Branch: main
- Last Pushed: 2022-08-26T16:59:45.000Z (almost 3 years ago)
- Last Synced: 2023-05-17T19:28:00.472Z (about 2 years ago)
- Language: Swift
- Homepage: https://www.pointfree.co/episodes/ep41-a-tour-of-snapshot-testing
- Size: 29.3 MB
- Stars: 0
- Watchers: 0
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- Contributing: CONTRIBUTING.md
- License: LICENSE
- Code of conduct: .github/CODE_OF_CONDUCT.md
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README
# 📸 SnapshotTesting
[](https://swift.org/download/)
[](https://actions-badge.atrox.dev/pointfreeco/swift-snapshot-testing/goto)
[](https://twitter.com/pointfreeco)
Delightful Swift snapshot testing.
## Usage
Once [installed](#installation), _no additional configuration is required_. You can import the `SnapshotTesting` module and call the `assertSnapshot` function.
``` swift
import SnapshotTesting
import XCTest
class MyViewControllerTests: XCTestCase {
func testMyViewController() {
let vc = MyViewController()
assertSnapshot(matching: vc, as: .image)
}
}
```
When an assertion first runs, a snapshot is automatically recorded to disk and the test will fail, printing out the file path of any newly-recorded reference.
> 🛑 failed - No reference was found on disk. Automatically recorded snapshot: …
>
> open "…/MyAppTests/\_\_Snapshots\_\_/MyViewControllerTests/testMyViewController.png"
>
> Re-run "testMyViewController" to test against the newly-recorded snapshot.
Repeat test runs will load this reference and compare it with the runtime value. If they don't match, the test will fail and describe the difference. Failures can be inspected from Xcode's Report Navigator or by inspecting the file URLs of the failure.
You can record a new reference by setting the `record` parameter to `true` on the assertion or setting `isRecording` globally.
``` swift
assertSnapshot(matching: vc, as: .image, record: true)
// or globally
isRecording = true
assertSnapshot(matching: vc, as: .image)
```
## Snapshot Anything
While most snapshot testing libraries in the Swift community are limited to `UIImage`s of `UIView`s, SnapshotTesting can work with _any_ format of _any_ value on _any_ Swift platform!
The `assertSnapshot` function accepts a value and any snapshot strategy that value supports. This means that a [view](Documentation/Available-Snapshot-Strategies.md#uiview) or [view controller](Documentation/Available-Snapshot-Strategies.md#uiviewcontroller) can be tested against an image representation _and_ against a textual representation of its properties and subview hierarchy.
``` swift
assertSnapshot(matching: vc, as: .image)
assertSnapshot(matching: vc, as: .recursiveDescription)
```
View testing is [highly configurable](Documentation/Available-Snapshot-Strategies.md#uiviewcontroller). You can override trait collections (for specific size classes and content size categories) and generate device-agnostic snapshots, all from a single simulator.
``` swift
assertSnapshot(matching: vc, as: .image(on: .iPhoneSe))
assertSnapshot(matching: vc, as: .recursiveDescription(on: .iPhoneSe))
assertSnapshot(matching: vc, as: .image(on: .iPhoneSe(.landscape)))
assertSnapshot(matching: vc, as: .recursiveDescription(on: .iPhoneSe(.landscape)))
assertSnapshot(matching: vc, as: .image(on: .iPhoneX))
assertSnapshot(matching: vc, as: .recursiveDescription(on: .iPhoneX))
assertSnapshot(matching: vc, as: .image(on: .iPadMini(.portrait)))
assertSnapshot(matching: vc, as: .recursiveDescription(on: .iPadMini(.portrait)))
```
> ⚠️ Warning: Snapshots may differ slightly unless compared on the same OS,
> device gamut, and scale as the simulator that originally took the reference.
> If this cannot be avoided, acceptance in differences can be configured by
> setting the `subpixelThreshold`-parameter.
>
> Example:
> ```swift
> // Allow each subpixel to deviate up to 5 byte-values
> assertSnapshot(matching: vc, as: .image(on: .iPhoneX, subpixelThreshold: 5))
> ```
>
Better yet, SnapshotTesting isn't limited to views and view controllers! There are [a number of available snapshot strategies](Documentation/Available-Snapshot-Strategies.md) to choose from.
For example, you can snapshot test URL requests (_e.g._, those that your API client prepares).
``` swift
assertSnapshot(matching: urlRequest, as: .raw)
// POST http://localhost:8080/account
// Cookie: pf_session={"userId":"1"}
//
// email=blob%40pointfree.co&name=Blob
```
And you can snapshot test `Encodable` values against their JSON _and_ property list representations.
``` swift
assertSnapshot(matching: user, as: .json)
// {
// "bio" : "Blobbed around the world.",
// "id" : 1,
// "name" : "Blobby"
// }
assertSnapshot(matching: user, as: .plist)
//
//
//
//
// bio
// Blobbed around the world.
// id
// 1
// name
// Blobby
//
//
```
In fact, _[any](Documentation/Available-Snapshot-Strategies.md#any)_ value can be snapshot-tested by default using its [mirror](https://developer.apple.com/documentation/swift/mirror)!
``` swift
assertSnapshot(matching: user, as: .dump)
// ▿ User
// - bio: "Blobbed around the world."
// - id: 1
// - name: "Blobby"
```
If your data can be represented as an image, text, or data, you can write a snapshot test for it! Check out [all of the snapshot strategies](Documentation/Available-Snapshot-Strategies.md) that ship with SnapshotTesting and [learn how to define your own custom strategies](Documentation/Defining-Custom-Snapshot-Strategies.md).
## Installation
### Xcode 11
> ⚠️ Warning: By default, Xcode will try to add the SnapshotTesting package to your project's main application/framework target. Please ensure that SnapshotTesting is added to a _test_ target instead, as documented in the last step, below.
1. From the **File** menu, navigate through **Swift Packages** and select **Add Package Dependency…**.
2. Enter package repository URL: `https://github.com/pointfreeco/swift-snapshot-testing.git`
3. Confirm the version and let Xcode resolve the package
4. On the final dialog, update SnapshotTesting's **Add to Target** column to a test target that will contain snapshot tests (if you have more than one test target, you can later add SnapshotTesting to them by manually linking the library in its build phase)
### Swift Package Manager
If you want to use SnapshotTesting in any other project that uses [SwiftPM](https://swift.org/package-manager/), add the package as a dependency in `Package.swift`:
```swift
dependencies: [
.package(
url: "https://github.com/pointfreeco/swift-snapshot-testing.git",
from: "1.9.0"
),
]
```
Next, add `SnapshotTesting` as a dependency of your test target:
```swift
targets: [
.target(name: "MyApp"),
.testTarget(
name: "MyAppTests",
dependencies: [
"MyApp",
.product(name: "SnapshotTesting", package: "swift-snapshot-testing"),
]
)
]
```
### Carthage
If you use [Carthage](https://github.com/Carthage/Carthage), you can add the following dependency to your `Cartfile`:
``` ruby
github "pointfreeco/swift-snapshot-testing" ~> 1.9.0
```
> ⚠️ Warning: Carthage instructs you to drag frameworks into your Xcode project. Xcode may automatically attempt to link these frameworks to your app target. `SnapshotTesting.framework` is only compatible with test targets, so when you first add it to your project:
>
> 1. Remove `SnapshotTesting.framework` from any non-test target it may have been added to.
> 2. Add `SnapshotTesting.framework` to any applicable test targets.
> 3. Add a **New Copy Build Phase** to any applicable test targets with **Destination** set to "Frameworks", and add `SnapshotTesting.framework` as an item to this phase.
> 4. Do _not_ add `SnapshotTesting.framework` to the "Input Files" or "Output Files" of your app target's Carthage `copy-frameworks` **Run Script Phase**.
>
> See Carthage's "[Adding frameworks to unit tests or a framework](https://github.com/Carthage/Carthage#adding-frameworks-to-unit-tests-or-a-framework)" documentation for more.
### CocoaPods
If your project uses [CocoaPods](https://cocoapods.org), add the pod to any applicable test targets in your `Podfile`:
```ruby
target 'MyAppTests' do
pod 'SnapshotTesting', '~> 1.9.0'
end
```
## Features
- [**Dozens of snapshot strategies**](Documentation/Available-Snapshot-Strategies.md). Snapshot testing isn't just for `UIView`s and `CALayer`s. Write snapshots against _any_ value.
- [**Write your own snapshot strategies**](Documentation/Defining-Custom-Snapshot-Strategies.md). If you can convert it to an image, string, data, or your own diffable format, you can snapshot test it! Build your own snapshot strategies from scratch or transform existing ones.
- **No configuration required.** Don't fuss with scheme settings and environment variables. Snapshots are automatically saved alongside your tests.
- **More hands-off.** New snapshots are recorded whether `isRecording` mode is `true` or not.
- **Subclass-free.** Assert from any XCTest case or Quick spec.
- **Device-agnostic snapshots.** Render views and view controllers for specific devices and trait collections from a single simulator.
- **First-class Xcode support.** Image differences are captured as XCTest attachments. Text differences are rendered in inline error messages.
- **Supports any platform that supports Swift.** Write snapshot tests for iOS, Linux, macOS, and tvOS.
- **SceneKit, SpriteKit, and WebKit support.** Most snapshot testing libraries don't support these view subclasses.
- **`Codable` support**. Snapshot encodable data structures into their [JSON](Documentation/Available-Snapshot-Strategies.md#json) and [property list](Documentation/Available-Snapshot-Strategies.md#plist) representations.
- **Custom diff tool integration**. Configure failure messages to print diff commands for [Kaleidoscope](https://kaleidoscope.app) (or your diff tool of choice).
``` swift
SnapshotTesting.diffTool = "ksdiff"
```
## Plug-ins
- [swift-snapshot-testing-nimble](https://github.com/Killectro/swift-snapshot-testing-nimble) adds [Nimble](https://github.com/Quick/Nimble) matchers for SnapshotTesting.
- [swift-html](https://github.com/pointfreeco/swift-html) is a Swift DSL for type-safe, extensible, and transformable HTML documents and includes an `HtmlSnapshotTesting` module to snapshot test its HTML documents.
- [GRDBSnapshotTesting](https://github.com/SebastianOsinski/GRDBSnapshotTesting) adds snapshot strategy for testing SQLite database migrations made with [GRDB](https://github.com/groue/GRDB.swift).
- [AccessibilitySnapshot](https://github.com/cashapp/AccessibilitySnapshot) adds easy regression testing for iOS accessibility.
- [AccessibilitySnapshotColorBlindness](https://github.com/Sherlouk/AccessibilitySnapshotColorBlindness) adds snapshot strategies for color blindness simulation on iOS views, view controllers and images.
- [swift-snapshot-testing-stitch](https://github.com/Sherlouk/swift-snapshot-testing-stitch/) adds the ability to stitch multiple UIView's or UIViewController's together in a single test.
Have you written your own SnapshotTesting plug-in? [Add it here](https://github.com/pointfreeco/swift-snapshot-testing/edit/master/README.md) and submit a pull request!
## Related Tools
- [`iOSSnapshotTestCase`](https://github.com/uber/ios-snapshot-test-case/) helped introduce screen shot testing to a broad audience in the iOS community. Experience with it inspired the creation of this library.
- [Jest](https://jestjs.io) brought generalized snapshot testing to the JavaScript community with a polished user experience. Several features of this library (diffing, automatically capturing new snapshots) were directly influenced.
## Learn More
SnapshotTesting was designed with [witness-oriented programming](https://www.pointfree.co/episodes/ep39-witness-oriented-library-design).
This concept (and more) are explored thoroughly in a series of episodes on [Point-Free](https://www.pointfree.co), a video series exploring functional programming and Swift hosted by [Brandon Williams](https://twitter.com/mbrandonw) and [Stephen Celis](https://twitter.com/stephencelis).
Witness-oriented programming and the design of this library was explored in the following [Point-Free](https://www.pointfree.co) episodes:
- [Episode 33](https://www.pointfree.co/episodes/ep33-protocol-witnesses-part-1): Protocol Witnesses: Part 1
- [Episode 34](https://www.pointfree.co/episodes/ep34-protocol-witnesses-part-1): Protocol Witnesses: Part 2
- [Episode 35](https://www.pointfree.co/episodes/ep35-advanced-protocol-witnesses-part-1): Advanced Protocol Witnesses: Part 1
- [Episode 36](https://www.pointfree.co/episodes/ep36-advanced-protocol-witnesses-part-2): Advanced Protocol Witnesses: Part 2
- [Episode 37](https://www.pointfree.co/episodes/ep37-protocol-oriented-library-design-part-1): Protocol-Oriented Library Design: Part 1
- [Episode 38](https://www.pointfree.co/episodes/ep38-protocol-oriented-library-design-part-2): Protocol-Oriented Library Design: Part 2
- [Episode 39](https://www.pointfree.co/episodes/ep39-witness-oriented-library-design): Witness-Oriented Library Design
- [Episode 40](https://www.pointfree.co/episodes/ep40-async-functional-refactoring): Async Functional Refactoring
- [Episode 41](https://www.pointfree.co/episodes/ep41-a-tour-of-snapshot-testing): A Tour of Snapshot Testing 🆓
## License
This library is released under the MIT license. See [LICENSE](LICENSE) for details.