Genything is a library dedicated to easy and composable generation of random data, no matter how complex.
Genything can be combined with Trickery which provides a growing library of pre-made generators which mock real-world information.
Both of these libraries may be used for code testing, rapid prototyping, demo applications, ui testing, and much more. Be creative!
- We do not include a dependency on XCTest
- Controllable randomness that's deterministic by default
- Produce the same results on CI, your colleagues machine, and your own
- You can use these generators for anything!
- Create dummy data for your example apps or to rapidly prototype features
- Use them in your SwiftUI previews to rapidly discover edge cases
- Run your screenshot tests with easy-to-use and predictable data
- Use your generators to unit test with Property Based Testing
- High test coverage
- 100% Documented
The Generator is the core of Genything.
public protocol Generator {
associatedtype T
func next(_ randomSource: RandomSource) -> T
}It defines a type with a function capable of generating values using a RandomSource.
The RandomSource is used to track and mutate any RandomNumberGenerator instance, allowing you to control just how much random you would like.
A generator of bools might look like this:
struct BoolGenerator: Generator {
func next(_ randomSource: RandomSource) -> T {
Bool.random(using: &randomSource.rng)
}
}or
AnyGenerator<Bool> { randomSource in
Bool.random(using: &randomSource.rng)
}Or, we can take advantage of Genything's arbitrary conformance for most standard Swift types (including Bool)
Bool.arbitraryGenything provides numerous ways to create your own Generators under the Generators namespace, and the Generator type is extended by many operators which you can use to further mutate and control the resulting generator.
The Arbitary protocol allows a Type to define a generator suitable for generating all of it's values.
Take Swift's Bool as example, it's Arbitrary is defined as:
extension Bool: Arbitrary {
public static var arbitrary: AnyGenerator<Bool> {
[true, false].arbitrary
}
}We can now use this definition automatically when we are composing a more complex arbitrary type:
struct Foo {
let bar: Bool
// ...
}
extension Transaction: Arbitrary {
public static var arbitrary: AnyGenerator<Bool> {
Gen.compose { generate in
Foo(
bar: generate(), // Will return true/false like a coin-flip for each generated value
//...
)
}
}
}These can then be used for invariant tests, to stub an API response, as preview data, etc...
Genything comes together with Trickery, a collection of generators suitable for producing pseudo-realistic data according to real-world-conditions rather than those enforced only by the type.
Consider a phone number. A phone number of type String has rules about length, formatting, allowable characters. Whereas the arbitrary type String contains contains at most a definition of it's length
Genything provides two extensions for XCTestCase which we suggest that you use as your primary method for property testing.
testAll(generator:config:file:line:body)testAllSatisfy(generator:config:file:line:predicate)
Checkout out our Playground guide
Genything is happy when combined with other open source libraries!
Generate arbitrary SFSymbols with SFSafeSymbols
Generate any SF Symbol
import SFSafeSymbols
let sfSymbolGen: AnyGenerator<SFSymbol> = SFSymbol.arbitrary.map { $0.rawValue }pod 'Genything'
pod 'Trickery' # Optional library of realistic fake data (Fake)
pod 'GenythingTest' # Optional extensions for property testing (testAll, testAllSatisfy)Create a Package.swift file in your root directory and add:
dependencies: [
.package(url: "https://github.com/justeattakeaway/genything.git", .upToNextMajor(from: "1.0.0"))
]Then add the packages you want to:
- General -> "Frameworks and Libraries", for an application of framework target
- Build Phases -> "Link Binary With Libraries", for a test target
The Genything project is owned and maintained by SkipTheDishes, a Just Eat Takeaway.com subsidiary.
Please read the Contribution Guide
Genything stands on the shoulder of giants. Please check out these other libraries and resources!
- SwiftCheck
- Fakery
- Point-Free's lessons on predictable randomness
- Kotest's Property Based Testing
See: License
Apache License Version 2.0, January 2004 http://www.apache.org/licenses/