Gollum

A Swift A/B testing framework for iOS

A/B testing (also known as split testing) is a good practice to test new concepts. Gollum is a A/B testing framework easy to use and inspired on some best practices in Swift, like:

Value Types (structs and enums)
Error Handling (ErrorType and throws)
Compile time feedback

Instalation (Cocoapods)

Add to your Podfile:

pod 'Gollum'

Then run the command below:

$ pod install

Usage

Create a enum with Version type for your A/B test. Pass on each case a string with version name (e.g. a) and its probability (e.g. 0.5), both separated by :.

enum MyABTest: Version {
    case a = "A:0.5"
    case b = "B:0.5"
}

try Gollum.instance.registerVersions([MyABTest.a, MyABTest.b])

After registration, you can check which version was selected using getSelectedVersion:

switch try Gollum.instance.getSelectedVersion(MyABTest.self) {
case .a:
    view.backgroundColor = UIColor.red
case .b:
    view.backgroundColor = UIColor.green
}

Or using isVersionSelected:

if try Gollum.instance.isVersionSelected(MyABTest.a) {
    view.backgroundColor = UIColor.red
} else if try Gollum.instance.isVersionSelected(MyABTest.b) {
    view.backgroundColor = UIColor.green
}

Error Handling

To avoid unexpected scenarios during an A/B testing, it's important treat errors. Gollum can throw these errors:

public enum GollumError: Error {
    case versionSyntaxError(String)
    case probabilitySumIncorrect(String)
    case emptyVersionArrayPassed(String)
    case selectedVersionNotFound(String)
}

If an A/B testing enum is created with wrong syntax, like missing version name or probability, the application will crash with error versionSyntaxError:

enum MyABTest: Version {
    case a = ":0.5"
    case b = "B:0.5"
}

Error message:

fatal error: 'try!' expression unexpectedly raised an error: Gollum.GollumError.versionSyntaxError("ABTest case expression must have name and probability values splitted by : (e.g. \"MyTestCaseA:0.5\")")

During an A/B test registration, the method registerVersions can throws emptyVersionArrayPassed, selectedVersionNotFound or probabilitySumIncorrect errors.

Also methods getSelectedVersion and isVersionSelected can throw selectedVersionNotFound error.

Objective-C

Because of some Swift's features, Gollum doesn't work in Objective-C.

License