Sleipnir presentation

Sleipnir
BDD style testing for Swift

Who we are
• Mobile team at railsware.com
• Open source fans railsware.github.io/

Outline
• What is BDD
• Testing in Swift - XCTest vs BDD style
• What Sleipnir is
• How to use it
• Questions

BDD
Behavior Driven Development

BDD
Behavior Driven Development
• BDD specifies that tests of any unit of software should be
specified in terms of the desired behaviour of the unit.
(from Wiki)
!
• BDD is all about specifications

BDD
describe("Calculator") {
!
describe("#add") {
!
it("returns the sum of its arguments") {
expect(Calculator().add(1, 2)).to(equal(3))
}
}
}

Testing in Swift - XCTest
class BookTest : XCTestCase {
func testPersonHasName() {
let person = Person(name: "John Doe”)
!
XCTAssertNotNil(person.name, "name should not be nil")
XCTAssertEqual(person.name, "John Doe", "incorrect name")
}
}

Testing in Swift - XCTest
class BookTest : XCTestCase {
func testPersonHasName() {
let person = Person(name: "John Doe”)
!
XCTAssertNotNil(person.name, "name should not be nil")
XCTAssertEqual(person.name, "John Doe", "incorrect name")
}
}
Does not specify behavior of the `Person` class

Testing in Swift - BDD
class PersonSpec : SleipnirSpec {
var personSpec = describe("Person") {
let person = Person(name: "John Doe")
context("name") {
it("should not be nil") {
expect(person.name).toNot(beNil())
}
it("should be correct") {
expect(person.name).to(equal("John Doe"))
}
}
}
}

Testing in Swift - BDD
Test code is a speciﬁcation of a class:
• Person name should not be nil
• Person name should be correct

Introducing Sleipnir
https://github.com/railsware/Sleipnir

What Sleipnir is
Mythological steed of Odin, Norse God

What Sleipnir is
BDD-style framework for Swift

What Sleipnir is
class HorseSpec : SleipnirSpec {
var spec = describe("Horse") {
context("usual") {
it("is not awesome") {
let usualHorse = UsualHorse()
expect(usualHorse.legsCount).to(equal(4))
usualHorse.isAwesome.should.beFalse()
}
}
context("Sleipnir") {
it("is awesome") {
let sleipnirHorse = Sleipnir()
expect(sleipnirHorse.legsCount).to(equal(8))
sleipnirHorse.isAwesome.should.beTrue()
}
}
}
}

Core principles
• Not using XCTest
• Pure Swift BDD testing framework
• Command line output
• Seeded random tests invocation

Running specs
1. Create a test target in Xcode
2. Invoke Runner.run() method in main.swift
3. Run test target

Running specs
Running With Random Seed: 7197
!
...F......
!
!
FAILURE Some spec should pass:
/Path/To/Your/Specs/SomeSpec.swift:27 Expected <1> to equal <3>
!
!
Finished in 0.0102 seconds
!
10 examples, 1 failures

Setup/Teardown blocks
• beforeEach { }
• afterEach { }
• beforeAll { }
• afterAll { }

Setup/Teardown blocks
let someSpec = describe("Some spec") {
var someArray: [Int]?
!
beforeEach {
someArray = [1, 2, 3]
}
afterEach {
someArray = nil
}
it("should pass") {
expect(someArray).toNot(beNil())
expect(someArray).to(contain(3))
}
}

Focused specs
Focus means “Run only focused stuff”
Useful in a project with a lot of specs

Focused specs
describe("Some spec") {
fit("focused") {
// WILL RUN
}
it("not focused") {
// WILL NOT RUN
}
}

Focused specs
fdescribe("focused group") {
// ...
}
!
fcontext("focused group") {
// ...
}
fit("focused example") {
// ...
}

Pending specs
Pending means “Don’t run this stuff”
Useful to denote an example that does not pass yet

Pending specs
xdescribe("Pending group") {
it("will not run") {
expect(false).to(beTrue())
}
it("is pending", PENDING)
}
Running With Random Seed: 2428
!
...P.......
!
PENDING Pending group is pending
!
!
Finished in 0.0062 seconds
!
11 examples, 0 failures, 1 pending

Shared example groups
Useful for extracting common specs
Allow to run same specs in different context

Shared example groups
sharedExamplesFor("some awesome stuff") {
(sharedContext : SharedContext) in
var stuff: Stuff?
beforeEach {
stuff = sharedContext()["stuff"] as Stuff
}
it("should be awesome") {
expect(stuff.awesome).to(beTrue())
}
}

Matchers
• equal
• beNil
• beFalse/beTrue
• beGreaterThan/beLessThan
expect(3).to(equal(3))
expect(3).toNot(beNil())
expect(true).to(beTrue())
expect(3).to(beGreaterThan(1))

Matchers on collections/strings
• contain
• beginWith/endWith
• beEmpty
expect([1,2,3]).to(contain(1,2))
expect("foobar").to(beginWith("foo"))
expect([1,2,3]).toNot(beEmpty())

Questions?
https://github.com/railsware/Sleipnir

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