Scala Testing

Links

https://www.scalatest.org/

Writing TDD unit tests with scalatest

At a Glance

Examples

libraryDependencies += "org.scalatest" %% "scalatest" % "2.2.6" % "test"

package com.acme.pizza

import org.scalatest.FunSuite
import org.scalatest.BeforeAndAfter

class PizzaTests extends FunSuite with BeforeAndAfter {

  var pizza: Pizza = _

  before {
    pizza = new Pizza
  }

  test("new pizza has zero toppings") {
    assert(pizza.getToppings.size == 0)
  }

  test("adding one topping") {
    pizza.addTopping(Topping("green olives"))
    assert(pizza.getToppings.size === 1)
  }

  // mark that you want a test here in the future
  test ("test pizza pricing") (pending)

}

Styles

FunSuite

import org.scalatest.FunSuite
class AddSuite extends FunSuite {
  test("3 plus 3 is 6") {
     assert((3 + 3) == 6)
  }
}

FlatSpec

The structure of this test is flat—like xUnit, but the test name can be written in specification style:

import org.scalatest.FlatSpec
class AddSpec extends FlatSpec {
  "Addition of 3 and 3" should "have result 6" in {
    assert((3 + 3) == 0)
  }
}

import collection.mutable.Stack
import org.scalatest._

class ExampleSpec extends FlatSpec with Matchers {

  "A Stack" should "pop values in last-in-first-out order" in {
    val stack = new Stack[Int]
    stack.push(1)
    stack.push(2)
    stack.pop() should be (2)
    stack.pop() should be (1)
  }

  it should "throw NoSuchElementException if an empty stack is popped" in {
    val emptyStack = new Stack[Int]
    a [NoSuchElementException] should be thrownBy {
      emptyStack.pop()
    }
  }
}

FeatureSpec

import org.scalatest._

class Calculator {
  def add(a:Int, b:Int): Int = a + b
}

class CalcSpec extends FeatureSpec with GivenWhenThen {
  info("As a calculator owner")
  info("I want to be able add two numbers")
  info("so I can get a correct result")
  feature("Addition") {
    scenario("User adds two numbers") {
      Given("a calculator")
      val calc = new Calculator
      When("two numbers are added")
      var result = calc.add(3, 3)
      Then("we get correct result")
       assert(result == 6)
    }
  }
}