Randomize — Delightfully Automatic Test Data for Swift

Randomize is your backstage magician for test data. A single macro turns empty models into living, breathing Swift objects with realistic values that actually look like something a human would type. It’s made for engineers who hate boilerplate but love precision — a fluent, expressive API that plays nice with SwiftUI, previews, and testing frameworks alike. You write the model; Randomize makes it come alive.

Designed natively for Apple platforms — pure Swift elegance, no runtime hacks, no regrets.

Highlights

• Zero-boilerplate generation with @Randomize
  Declare your type, mark it up, and watch it populate itself. No manual builders, no factory clutter — just clean Swift that reads like you always wanted it to.

• Fine-grained control with @Randomizable(in:) and @Unrandomizable
  Set ranges, boundaries, and constraints for each property. You’re still the director; the macro’s just your very efficient assistant who never mistypes.

• Safe ranges for numerics, dates, strings, and CoreGraphics types
  Smart defaults ensure generated values feel natural and stay valid. Your previews and test runs look realistic — not like a math problem gone rogue.

• Pure Swift, macro-based expansion — readable, inspectable, and fast
  No black boxes. Everything expands at compile time, so you can inspect the generated code like a pro. Performance stays razor-sharp, just like your build times.

• Perfect for SwiftUI Previews, tests, fixtures, and demo data
  Whether you’re mocking a UI, seeding tests, or faking data for a pitch demo, Randomize keeps it clean, quick, and aesthetic. Less typing, more shipping.

Quick Look

Below are real-world scenarios that show how Randomize accelerates your day-to-day work.

1. SwiftUI Preview with realistic content density

@Randomize
struct Article {
    @Randomizable(in: 20..<80) var title: String     // length 20–79
    @Randomizable(in: 140..<400) var summary: String // length 140–399
    var heroImage: UIImage
}

struct ArticleRow: View {
    let article: Article
    var body: some View {
        VStack(alignment: .leading, spacing: 8) {
            Image(uiImage: article.heroImage)
                .resizable().scaledToFill().frame(height: 180).clipped()
            Text(article.title).font(.headline)
            Text(article.summary).font(.subheadline).foregroundStyle(.secondary)
        }
        .padding()
    }
}

#Preview("Randomized Article") {
    ArticleRow(article: .random())
}

Random generation build flag

⚠️ Important change in the latest version: the Randomize macro only generates random data when the RANDOMIZING build flag is explicitly enabled.

This is intentional. The goal is to ensure that random data generation can never accidentally leak into production builds and is always a conscious developer choice.

Xcode target

Add the flag to the appropriate target:

1. Target ➝ Build Settings
2. Other Swift Flags
3. Add:

-D RANDOMIZING

It is strongly recommended to enable this only for Debug configurations.

Swift Package Manager (SPM) module

For SPM targets, define the flag using swiftSettings:

.target(
    name: "YourModule",
    dependencies: ["Randomize"],
    swiftSettings: [
        .define("RANDOMIZING")
    ]
)

If the flag is not present, the @Randomize macro does not generate random initializers, keeping behavior deterministic and production-safe.

This approach ensures that Randomize does its magic where it belongs (previews, tests, demo data), and stays completely silent where it does not.