A library for easily generating automatic Playbook (Demo) view and Tests using SwiftUI Preview

Works with: UI-components, screens and flows

Prefire

Do you like SwiftUI Preview and use it? Then you must try 🔥Prefire!

You can try 🔥Prefire starting from example project.

• ✅ Easy to use: Get started with the example project.
• ✅ Fully automatic generation based on Sourcery
• ✅ Generation Playbook (Demo) views
• ✅ Generation Snapshot tests based on swift-snapshot-testing
• ✅ Generation Accesability Snapshot tests
• ✅ Support for Xcode Plugin

---

Installation

Prefire can be installed for an Xcode Project or only for one Package.

Xcode Project Plugin

You can integrate Prefire as an Xcode Build Tool Plug-in if you're working on a project in Xcode.

1. Add Prefire as a package dependency to your project without linking any of the products.

2. Select the target to which you want to add linting and open the Build Phases inspector. Open Run Build Tool Plug-ins and select the + button. From the list, select PrefirePlaybookPlugin or PrefireTestsPlugin, and add it to the project.

Swift Package Plugin

You can integrate Prefire as a Swift Package Manager Plug-in if you're working with a Swift Package with a Package.swift manifest.

1. Add Prefire as a package dependency to your Package.swift file.

dependencies: [
    .package(url: "https://github.com/BarredEwe/Prefire", from: "1.0.0")
]

2. Add Prefire to a target using the plugins parameter.

.target(
    plugins: [
        // For Playbook (Demo) view
        .plugin(name: "PrefirePlaybookPlugin", package: "Prefire")
    ]
),
.testTarget(
    plugins: [
        // For Snapshot Tests
        .plugin(name: "PrefireTestsPlugin", package: "Prefire")
    ]
)

---

Usage

To generate tests and playbook, simply mark your preview using the PrefireProvider protocol:

struct Text_Previews: PreviewProvider, PrefireProvider {
    static var previews: some View { ... }
}

If you use the #Preview macro, 🔥Prefire will automatically find it!

If you don't need it, mark view - .prefireIgnored():

#Preview {
    Text("")
        .prefireIgnored()
}

If you want to disable the automatic get of all previews, use the setting preview_default_enabled: false. Then to include preview in the test, you need to call the .prefireEnabled():

#Preview {
    Text("")
        .prefireEnabled()
}

Playbook (Demo) View

To use Playbook, simply use PlaybookView

• If you want to see a list of all the Views, use isComponent: true
• If you want to sort by UserStory, use isComponent: false

import Prefire 

struct ContentView: View {
    var body: some View {
        PlaybookView(isComponent: true, previewModels: PreviewModels.models)
    }
}

Snapshot tests

Just run generated tests 🚀 All tests will be generated in the DerivedData folder.

Plugin PrefireTestsPlugin will handle everything for you 🛠️

For detailed instruction, check out swift-snapshot-testing or examine an example project.

---

API

Prefire provide new commands for previews:

• You can set the delay, precision and perceptualPrecision parameters for the snapshot:

  .snapshot(delay: 0.3, precision: 0.95, perceptualPrecision: 0.98)

  static var previews: some View {
      TestView()
          .snapshot(delay: 0.3, precision: 0.95, perceptualPrecision: 0.98)
  }

• Function for connecting preview together in one Flow:

  

  .previewUserStory(.auth)

  static var previews: some View {
      PrefireView()
          .previewUserStory(.auth)
  }
  
  static var previews: some View {
      AuthView()
          .previewUserStory(.auth)
  }

  For example Authorization flow: LoginView, OTPView and PincodeView

  
  

• If a preview contains more than one View, you can mark State for these views.

  

  .previewState(.loading)

  static var previews: some View {
      TestView("Default")
  
      TestView("Loading")
          .previewState(.loading)
  }

  
  

---

Config

To further customize Prefire, you can create a .prefire.yml file in the root directory of your project. Here's an example of its content:

test_configuration:
  - target: PrefireExample 
  - test_file_path: PrefireExampleTests/PreviewTests.generated.swift
  - template_file_path: CustomPreviewTests.stencil
  - simulator_device: "iPhone15,2"
  - required_os: 16
  - preview_default_enabled: true
  - sources:
    - ${PROJECT_DIR}/Sources/
  - snapshot_devices:
  	- iPhone 14
  	- iPad
  - imports:
    - UIKit
    - SwiftUI
  - testable_imports:
    - Prefire

playbook_configuration:
  - preview_default_enabled: true
  - template_file_path: CustomModels.stencil
  - imports:
    - UIKit
    - Foundation
  - testable_imports:
    - SwiftUI

Configuration keys and their descriptions

• target - Your project Target for Snapshot tests. Default: FirstTarget
• test_file_path - Filepath to generated file. Default: DerivedData
• template_file_path - Stencil file for generated file. Optional parameter.
  For test plugin Default: Templates/PreviewTests.stencil from the package.
  For playbook plugin Default: Templates/PreviewModels.stencil from the package
• simulator_device - Device for Snapshot testing. Optional parameter.
• required_os - iOS version for Snapshot testing. Optional parameter.
• snapshot_devices - the list of devices snapshots should be generated for. The simulator_device specified above will still be required and used, but snapshotting will take on the traits of the snapshot_devices. The displayScale will default to 2.0 and device specific safe areas will be .zero. Optional parameter.
• preview_default_enabled - Do I need to automatically add all previews based on the new syntax to the tests. Default: true
• imports - Additional imports for the generated Playbook/Tests. Optional parameter.
• testable_imports - Additional @testable imports for the generated Playbook/Tests. Optional parameter.
• sources - Paths to swift file or directory sources. Default: File paths of a specific target or project

Distribution

When preparing for distribution, you may want to exclude your PreviewProvider and mock data from release builds. This can be achieved by wrapping them in #if DEBUG compiler directives. Alternatively, you can pass a compiler flag to exclude PreviewModels from release builds.

To exclude PreviewModels using Swift Package Manager, pass the PLAYBOOK_DISABLED swift setting in the package that links PrefirePlaybookPlugin:

swiftSettings: [
    .define("PLAYBOOK_DISABLED", .when(configuration: .release)),
]

If you are using Xcode, you can pass the compiler flag in the Xcode build settings:

SWIFT_ACTIVE_COMPILATION_CONDITIONS = PLAYBOOK_DISABLED;

Requirements

• Swift 5.6 or higher
• Xcode 14.0 or higher
• iOS 14 or higher

Troubleshooting

NavigationView in Preview not supported for Playbook

• Consider using other views or layouts for your Playbook needs.

Running Prefire via CI

• To run Prefire via Continuous Integration (CI), you need to configure permissions: defaults write com.apple.dt.Xcode IDESkipPackagePluginFingerprintValidatation -bool YES

Xcode is unable to generate tests in a custom path.

• To resolve this, you’ll need to disable the sandbox for file generation by running the following command in your terminal: defaults write com.apple.dt.Xcode IDEPackageSupportDisablePluginExecutionSandbox -bool YES