Specs² Integration

Getting started

Accord provides Specs² matchers on validation results; the intended use case is to be able to write a test spec for your domain model and its associated validation rules. To enable Specs² integration, add a dependency on the accord-specs2 module:

Using sbt

Add the following to your build.sbt or to the settings in your Scala build configuration:

libraryDependencies += "com.wix" %% "accord-specs2" % "0.3.1" % "test"

Using Maven

Add the following to your POM:

<dependency>
    <groupId>com.wix</groupId>
    <artifactId>accord-specs2_${scala.tools.version}</artifactId>
    <version>0.3.1</version>
    <scope>test</scope>
</dependency>

API

All matchers are provided by the com.wix.accord.specs2.ResultMatchers trait. Simply mix it into your suite or spec as follows:

import org.specs2.mutable.Specification
import com.wix.accord._
import com.wix.accord.specs2.ResultMatchers

class DomainValidationSpec extends Specification with ResultMatchers {
  // Your tests...
}

As an example, consider the following domain model:

import com.wix.accord.dsl._

object PrimitiveSchema {
  case class Person( firstName: String, lastName: String )
  case class Classroom( teacher: Person, students: Seq[ Person ] )

  implicit val personValidator = validator[ Person ] { p =>
    p.firstName is notEmpty
    p.lastName is notEmpty
  }

  implicit val classValidator = validator[ Classroom ] { c =>
    c.teacher is valid
    c.students.each is valid
    c.students have size > 0
  }
}

All subsequent examples will refer to this domain model.

Testing success/failure

To test a validation result for success, simply use the provided succeed matcher:

"The Person validator" should {
  "succeed on a valid Person object" in {
    val sample = Person( "Wernher", "von Braun" )
    val result = validate( sample )
    result should succeed
  }
}

Likewise, the provided fail matcher can be used to ensure that a validation has failed:

"The Person validator" should {
  "fail on a Person with an empty first name" in {
    val sample = Person( "", "Last name" )
    val result = validate( sample )
    result should fail
  }
}

Testing rule violations

Sometimes merely asserting a validation failure is not enough. Accord also lets you match on the actual violation messages via the failWith helper and a simple DSL:

"The Person validator" should {
  "render a correct violation for a Person with an empty first name" {
    val sample = Person( "", "Last name" )
    val result = validate( sample )
    result should failWith( "firstName" -> "must not be empty" )
  }
}

Behind the scenes, the failWith helper takes one or more matchers on violations, and wraps them to provide a single matcher on Result. The "firstName" -> "must not be empty" syntax actually uses an implicit conversion to construct a RuleViolationMatcher; the full syntax enables you to explicitly match on any part of the violation:

val matchByValue       = RuleViolationMatcher( value       = ""                  )
val matchByDescription = RuleViolationMatcher( description = "firstName"         )
val matchByConstraint  = RuleViolationMatcher( constraint  = "must not be empty" )

// You can specify any combination of these requirements, so the following is
// equivalent to the "firstName" -> "must not be empty" syntax:
val expectedViolation = RuleViolationMatcher(
  description = "firstName",
  constraint = "must not be empty" )

Testing group violations

Group violations are relatively rare, and are used to specify that multiple rules have failed with some sort of semantic relation between them. One example is the Valid combinator, which enables composition; in the example domain, a Classroom is only considered valid if its teacher (a Person) is also valid. The Person validator defines a number of rules, any of which may be violated by a specific teacher. These violations are all grouped together under a single violation, which you can test with the group helper:

"The Classroom validator" should {
  "fail a classroom with an invalid teacher" in {
    val sample = Classroom( Person( "", "" ), Seq( Person( "Alfred", "Aho" ) ) )
    val result = validate( sample )
    result should failWith( group( "teacher", "is invalid",
      "firstName" -> "must not be empty",
      "lastName" -> "must not be empty"
    ) )
  }
}

As with rule violations, the group helper simply provides a more concise API to create a GroupViolationMatcher. In practice this is equivalent to:

val expectedViolation = GroupViolationMatcher(
  description = "teacher",
  constraint = "is invalid",
  violations = Seq(
    RuleViolation( description = "firstName", constraint = "must not be empty" ),
    RuleViolation( description = "lastName",  constraint = "must not be empty" ),
  ) )
result should failWith( expectedViolation )