mattrubin / Guanaco

Nimble matchers for Result.

Guanaco

Nimble matchers for Result.

let result: Result<String, NSError> = success("llama")
expect(result).to(haveSucceeded())
expect(result).to(haveSucceeded(equal("llama")))

let error = NSError(domain: "guanaco", code: 10, userInfo: [NSLocalizedDescriptionKey: "lama guanicoe"])
let result: Result<String, NSError> = failure(error)
expect(result).to(haveFailed())
expect(result).to(haveFailed(beAnError(
  domain: equal("guanaco"),
  code: beGreaterThan(0),
  localizedDescription: match("guanicoe")
)))

Why Use Guanaco: Testing Algebraic Data Types

Swift makes it easy to define ADTs, or "algebraic data types". The canonical example of an algebraic data type is Result Result<ValueType, ErrorType> enum, which represents the result of some operation. When the operation is successful, the Result provides a value of type ValueType. When it is not, it provides a value of type ErrorType:

switch result {
 case .Success(let value): /* ... */
 case .Failure(let error): /* ... */
}

Unfortunately, testing algebraic data types like Result can be a pain. For example, if you had a result of type Result<Int, NSError>, and wanted to test that it had a successful value of 10, you'd have to write:

switch result {
 case .Success(let value): XCTAssertEquals(value, 10)
 case .Failure(let error): XCTFail()
}

Tests should be clear, consise, and provide useful failure messages--in other words, the code above isn't going to cut it! Instead, use Guanaco to write:

expect(result).to(haveSucceeded(equal(10)))

How to Install

CocoaPods

# Podfile

pod 'Guanaco', :git => 'https://github.com/modocache/Guanaco.git'

Git Submodules

First, add Guanaco as a Git submodule. From within your Git repository, open the command line and run:

$ git submodule add \
    https://github.com/modocache/Guanaco.git \
    External/Guanaco # Specify any path you like here

Open the .xcworkspace for your project and add Guanaco.xcodeproj to your workspace. Then, add Guanaco-OSX.framework or Guanaco-iOS.framework to your test target's "Link Binary with Libraries" build phase.