Jasmine-style BDD tests in Scala

I write a lot of JavaScript these days and got quite accustomed to Jasmine-style unit tests with their expressiveness and flexibility. I also code a fair amount of Scala and one thing I miss every time I switch is a good support for BDD. I use ScalaTest and it is a powerful framework but one thing it is missing for years is the support for hierarchical specs. Namely, the analog of Jasmine’s “beforeEach” and “afterEach” in nested “describe”s. So recently, after struggling once again to express a test concisely, I felt that enough was enough. Here is a FunSpec extension trait I came up with:

	package com.prystupa
	import org.scalatest.{Tag, FunSpec}
	import scala.collection.mutable
	trait JasmineSpec extends FunSpec {
	private val itWord = new ItWord
	private val setup: mutable.Stack[List[() => Unit]] = mutable.Stack()
	private val tearDown: mutable.Stack[List[() => Unit]] = mutable.Stack()
	protected def beforeEach(code: => Unit) {
	val list = (() => code) :: setup.pop()
	setup.push(list)
	}
	protected def afterEach(code: => Unit) {
	val list = (() => code) :: tearDown.pop()
	tearDown.push(list)
	}
	protected override def describe(description: String)(fun: => Unit) {
	setup.push(List())
	tearDown.push(List())
	super.describe(description)(fun)
	tearDown.pop()
	setup.pop()
	}
	protected override val it = observe
	private lazy val observe: ItWord = new ItWord {
	override def apply(specText: String, testTags: Tag*)(testFun: => Unit) {
	val before = setup.reverse.flatMap(_.reverse)
	val after = tearDown.flatMap(_.reverse)
	itWord(specText, testTags: _*) {
	before.foreach(_())
	testFun
	after.foreach(_())
	}
	}
	}
	}

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JasmineSpec.scala

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When mixed in, the trait intercepts FunSpec’s “describe”s to keep track of all the “beforeEach” and “afterEach” on every nesting level. It also overrides FunSpec’s “it” to execute appropriate setup and tear-down code for that “it” before running the test. And here is a contrived example of using it in Scala:

	package com.prystupa
	import org.scalatest.matchers.ShouldMatchers
	import org.junit.runner.RunWith
	import org.scalatest.junit.JUnitRunner
	/**
	* Created with IntelliJ IDEA.
	* User: eprystupa
	* Date: 8/24/13
	* Time: 11:37 PM
	*/
	@RunWith(classOf[JUnitRunner])
	class MathSuite extends JasmineSpec with ShouldMatchers {
	var x: Int = _
	var result: Int = _
	describe("A simple calculator") {
	describe("when turned on") {
	it("displays 0") {
	result should equal(0)
	}
	describe("when I input 5") {
	beforeEach {
	x = 5
	}
	describe("and multiple by 3") {
	beforeEach {
	result = x * 3
	}
	it("shows 15") {
	result should equal(15)
	}
	}
	describe("and add by 3") {
	beforeEach {
	result = x + 3
	}
	it("shows 8") {
	result should equal(8)
	}
	}
	}
	}
	}
	}

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MathSuite.scala

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For a complete project that you can explore or execute with maven look here: https://github.com/prystupa/jasmine-spec-scala