Rule request: quick_discouraged_focused_test

[ornithocoder]

It's quite common - in large test suites - the usage of focused test (fdescribe, fcontext, and fit), especially when doing TDD.

Focused test is a pretty handy feature, but not rarely do developers push code with focused test without realizing it :-(

This rule would trigger a warning for focused tests, to remind developers they have focused tests.

Non Triggering Examples

class TotoTests: QuickSpec {
   override func spec() {
       describe("foo") {
           describe("bar") { } 
           context("bar") {
               it("bar") { }
           }
           it("bar") { }
           itBehavesLike("bar")
       }
   }
}

Triggering Examples

class TotoTests: QuickSpec {
   override func spec() {
       ↓fdescribe("foo") {
       }
   }
}

class TotoTests: QuickSpec {
   override func spec() {
       ↓fcontext("foo") {
       }
   }
}

class TotoTests: QuickSpec {
   override func spec() {
       ↓fit("foo") {
       }
   }
}

class TotoTests: QuickSpec {
   override func spec() {
       describe("foo") {
           ↓fit("bar") { }
       }
   }
}

class TotoTests: QuickSpec {
   override func spec() {
       context("foo") {
           ↓fit("bar") { }
       }
   }
}

class TotoTests: QuickSpec {
   override func spec() {
       describe("foo") {
           context("bar") {
               ↓fit("toto") { }
            }
        }
    }
}

class TotoTests: QuickSpec {
   override func spec() {
       ↓fitBehavesLike("foo")
   }
}

[jpsim]

Done in #1906.