SwiftSnapshotTesting

This project’s purpose is to simplify UI testing on iOS.

SwiftSnapshotTesting helps to check application’s UI with a few lines of code. No need to manually manage reference images any more.

This framework is able to:

take a screenshot of a full screen, screen without status bar or any XCUIElement individually
record the screenshot on your Mac
compare and highlight the difference between new screenshots and previously recorded ones using Metal

Internally SwiftSnapshotTesting operates with MTLTextures during the snapshot comparison. Also it uses Resources Bridge Monitor app to read and write files on Mac.

⚠️ Currently this project is in early alfa stage and it’s a subject for improvements.

Requirements

Swift 5.2
iOS 11.0

Install via SwiftPM

.package(url: "https://github.com/eugenebokhan/SwiftSnapshotTesting.git",
         .upToNextMinor(from: "0.1.6"))

How To Use

Create a subclass of SnapshotTestCase

class MyCoolUITest: SnapshotTestCase { ...

Choose folder on your Mac to store the reference snapshots by overriding snapshotsReferencesFolder variable
```
override var snapshotsReferencesFolder: String {
    "/Path-To-Snapshots-Folder/"
}
```

Assert UI element
```
assert(element: XCUIElement,
       testName: String,
       ignore rects: Set<CGRect>,
       configuration: Configuration,
       recording: Bool) throws
```
- element - element to compare.
- testName - name of the test. It will be used in the name of the reference image file
- rects - rects (possible subviews’ frames) to ignore.
- configuration current test configuration.
- recording - by setting true this argument you will record the reference snapshot. By setting false you will compare the element with previously recorded snapshot.

Assert screenshot

assert(screenshot: XCUIScreenshot,
       testName: String,
       ignore ignorables: Set<Ignorable>,
       configuration: Configuration,
       recording: Bool) throws

screenshot - screenshot to test.
ignorables - UI elements to ignore. Ignorable can be XCUIElement, custom CGRect or predefined .statusBar.

Info.plist configuration

In order for SwiftSnapshotTesting to work when running on iOS 14, you will have to include two keys in your app’s Info.plist file. The keys are Privacy - Local Network Usage Description (NSLocalNetworkUsageDescription) and Bonjour services (NSBonjourServices). For the privacy key, include a human-readable description of what benefit the user gets by allowing your app to access devices on the local network. The Bonjour services key is an array of service types that your app will browse for. For SwiftSnapshotTesting, he value of this key should be _ResourcesBridge._tcp.

If you do not configure the above keys properly, then SwiftSnapshotTesting won’t work on real devices.

XCTAttachment

After each assertion test SnapshotTestCase provides an attachment containing per-pixel L2 distance between snapshot and the corresponding reference and MTLTexture with highlighted difference. You are able to look at the diff using MTLTextureViewer.

Example

Your can find a small example of usage of SwiftSnapshotTesting in the ImageFlip repo.

License

MIT