Informer

Trait to which custom information about a running suite of tests can be reported.

An Informer is essentially used to wrap a Reporter and provide easy ways to send custom information to that Reporter via an InfoProvided event. Informer contains an apply method that takes an object. The Informer will invoke toString on the passed object and forward the resulting string to the Reporter as the message parameter of an InfoProvided event.

Here's an example of using an Informer in a Suite subclass:

import org.scalatest._

class MySuite extends Suite {
  def testAddition(info: Informer) {
    assert(1 + 1 === 2)
    info("Addition seems to work")
  }
}

If you run this Suite from the interpreter, you will see the message included in the printed report:

scala> (new MySuite).execute()
Test Starting - MySuite.testAddition(Reporter)
Info Provided - MySuite.testAddition(Reporter): Addition seems to work
Test Succeeded - MySuite.testAddition(Reporter)

Traits FunSuite, FunSpec, FlatSpec, WordSpec, FeatureSpec, and their sister traits in org.scalatest.fixture package declare an implicit info method that returns an Informer. This implicit info is used, for example, to enable the syntax offered by the GivenWhenThen trait, which contains methods that take an implicit Informer. Here's an example of a FeatureSpec that mixes in GivenWhenThen:

import org.scalatest.FeatureSpec
import org.scalatest.GivenWhenThen

class ArithmeticSpec extends FeatureSpec with GivenWhenThen {

  feature("Integer arithmetic") {

    scenario("addition") {

      given("two integers")
      val x = 2
      val y = 3

      when("they are added")
      val sum = x + y

      then("the result is the sum of the two numbers")
      assert(sum === 5)
    }

    scenario("subtraction") {

      given("two integers")
      val x = 7
      val y = 2

      when("one is subtracted from the other")
      val diff = x - y

      then("the result is the difference of the two numbers")
      assert(diff === 5)
    }
  }
}

Were you to run this FeatureSpec in the interpreter, you would see the following messages included in the printed report:

scala> (new ArithmeticFeatureSpec).run()
Feature: Integer arithmetic
  Scenario: addition
    Given two integers
    When they are added
    Then the result is the sum of the two numbers
  Scenario: subtraction
    Given two integers
    When one is subtracted from the other
    Then the result is the difference of the two numbers