This introduces a base generic behavior definition which can be extended with a specified context type.

Currently, shared assertions implementation using "shared examples" suffers from two drawbacks:

• Defined in QuickConfiguration subclass. A file that initially intended for configuration how Quick behaves, "shared examples" are added here to allow their discovery during setup time.
• Receives a context of [String: Any], which is string-typed and erase any type information of the context elements.

The proposed solution is to introduce Behavior<Context> which will address these issues by allowing user to define subclasses for each "shared example" with a specific context type and a similar structure to QuickSpec

The example below demonstrates how it might be used:

import Quick
import Nimble

struct EdibleContext {
   let edible: Edible
}

class EdibleBehavior: Behavior<EdibleContext> {
   override class func spec(_ aContext: @escaping () -> EdibleContext) {
      var sut: Edible!
      beforeEach {
         sut = aContext().edible
      }
      beforeEach {
         sut = nil
      }
      it("makes dolphins happy") {
        let dolphin = Dolphin(happy: false)
        dolphin.eat(sut)
        expect(dolphin.isHappy).to(beTruthy())
      }
   } 
}

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

    itBehavesLike(EdibleBehavior.self) { EdibleContext(edible: mackerel) }
  }
}

Checklist - While not every PR needs it, new features should consider this list:

• Does this have tests? Yes
• Does this have documentation? Yes
• Does this break the public API (Requires major version bump)? No
• Is this a new feature (Requires minor version bump)? Yes