Reducing Test Boilerplate with Shared Assertions

In some cases, the same set of specifications apply to multiple objects.

For example, consider a protocol called Edible. When a dolphin eats something Edible, the dolphin becomes happy. Mackerel and Cod are both edible. Quick allows you to easily test that a dolphin is happy to eat either one.

swift

protocol Edible { }

class Dolphin {
  private(set) var isHappy: Bool

  init(happy: Bool) {
    self.isHappy = happy
  }

  /// Makes Doplhin happy
  func eat(_ edible: Edible) {
    isHappy = true
  }
}

class Mackerel: Edible { }
class Cod: Edible { }

Behavior<Context>

The code below defines a Behavior object with a set of reusable examples. It also specifies that both mackerel and cod behave like SomethingEdible:

swift

class SomethingEdible: Behavior<Edible> {
  override class func spec(_ aContext: @escaping () -> Edible) {
    var edible: Edible!
    beforeEach {
      edible = aContext()
    }

    it("makes dolphins happy") {
      let dolphin = Dolphin(happy: false)
      dolphin.eat(edible)
      expect(dolphin.isHappy).to(beTruthy())
    }
  }
}

class MackerelSpec: QuickSpec {
  override class func spec() {
    var mackerel: Mackerel!
    beforeEach {
      mackerel = Mackerel()
    }

    itBehavesLike(SomethingEdible.self) { mackerel }
  }
}

class CodSpec: QuickSpec {
  override class func spec() {
    var cod: Cod!
    beforeEach {
      cod = Cod()
    }

    itBehavesLike(SomethingEdible.self) { cod }
  }
}

Because Behavior<Context> uses Swift generics, it's not possible to use it from Objective-C.

Shared Examples

The example below defines a set of "shared examples" for "something edible", and specifies that both mackerel and cod behave like "something edible":

swift

// Swift

import Quick
import Nimble

class EdibleSharedExamplesConfiguration: QuickConfiguration {
  override class func configure(_ configuration: Configuration) {
    sharedExamples("something edible") { (sharedExampleContext: @escaping SharedExampleContext) in
      it("makes dolphins happy") {
        let dolphin = Dolphin(happy: false)
        let edible = sharedExampleContext()["edible"]
        dolphin.eat(edible)
        expect(dolphin.isHappy).to(beTruthy())
      }
    }
  }
}

class MackerelSpec: QuickSpec {
  override class func spec() {
    var mackerel: Mackerel!
    beforeEach {
      mackerel = Mackerel()
    }

    itBehavesLike("something edible") { ["edible": mackerel] }
  }
}

class CodSpec: QuickSpec {
  override class func spec() {
    var cod: Cod!
    beforeEach {
      cod = Cod()
    }

    itBehavesLike("something edible") { ["edible": cod] }
  }
}

objc

// Objective-C

@import Quick;
@import Nimble;

QuickConfigurationBegin(EdibleSharedExamplesConfiguration)

+ (void)configure:(Configuration *configuration) {
  sharedExamples(@"something edible", ^(QCKDSLSharedExampleContext exampleContext) {
    it(@"makes dolphins happy", ^{
      Dolphin *dolphin = [[Dolphin alloc] init];
      dolphin.happy = NO;
      id<Edible> edible = exampleContext()[@"edible"];
      [dolphin eat:edible];
      expect(dolphin.isHappy).to(beTruthy())
    });
  });
}

QuickConfigurationEnd

QuickSpecBegin(MackerelSpec)

__block Mackerel *mackerel = nil;
beforeEach(^{
  mackerel = [[Mackerel alloc] init];
});

itBehavesLike(@"something edible", ^{ return @{ @"edible": mackerel }; });

QuickSpecEnd

QuickSpecBegin(CodSpec)

__block Mackerel *cod = nil;
beforeEach(^{
  cod = [[Cod alloc] init];
});

itBehavesLike(@"something edible", ^{ return @{ @"edible": cod }; });

QuickSpecEnd

Shared examples can include any number of it, context, and describe blocks. They save a lot of typing when running the same tests against several different kinds of objects.

In some cases, you won't need any additional context. In Swift, you can simply use sharedExamples closures that take no parameters. This might be useful when testing some sort of global state:

swift

// Swift

import Quick

sharedExamples("everything under the sea") {
  // ...
}

itBehavesLike("everything under the sea")

In Objective-C, you'll have to pass a block that takes a QCKDSLSharedExampleContext, even if you don't plan on using that argument. Sorry, but that's the way the cookie crumbles! :cookie: :bomb:

You can also "focus" shared examples using the fitBehavesLike function.