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  • package org
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  • package scalatest

    ScalaTest's main traits, classes, and other members, including members supporting ScalaTest's DSL for the Scala interpreter.

    ScalaTest's main traits, classes, and other members, including members supporting ScalaTest's DSL for the Scala interpreter.

    Definition Classes
    org
  • trait LoneElement extends AnyRef

    Trait that provides an implicit conversion that adds to collection types a loneElement method, which will return the value of the lone element if the collection does indeed contain one and only one element, or throw TestFailedException if not.

    Trait that provides an implicit conversion that adds to collection types a loneElement method, which will return the value of the lone element if the collection does indeed contain one and only one element, or throw TestFailedException if not.

    This construct allows you to express in one statement that a collection should contain one and only one element and that the element value should meet some expectation. Here's an example:

    set.loneElement should be > 9

    Or, using an assertion instead of a matcher expression:

    assert(set.loneElement > 9)

    The loneElement syntax can be used with any collection type C for which an implicit Collecting[C] is available. ScalaTest provides implicit Collecting instances for scala.collection.GenTraversable, Array, and java.util.Collection. You can enable the loneElement syntax on other collection types by defining an implicit Collecting instances for those types.

    If you want to use loneElement with a java.util.Map, first transform it to a set of entries with entrySet, and if helpful, use ScalaTest's Entry class:

    scala> import org.scalatest._
import org.scalatest._

scala> import LoneElement._
import LoneElement._

scala> import Matchers._
import Matchers._

scala> val jmap = new java.util.HashMap[String, Int]
jmap: java.util.HashMap[String,Int] = {}

scala> jmap.put("one", 1)
res0: Int = 0

scala> jmap.entrySet.loneElement should be (Entry("one", 1))

    Definition Classes
    scalatest
  • LoneElementCollectionWrapper
  • LoneElementJavaMapWrapper
  • LoneElementStringWrapper
c

org.scalatest.LoneElement

LoneElementCollectionWrapper

final class LoneElementCollectionWrapper[E, CTC[_]] extends AnyRef

Wrapper class that adds a loneElement method to any collection type C for which an implicit Collecting[C] is available.

Through the implicit conversion provided by trait LoneElement, this class allows you to make statements like:

trav.loneElement should be > 9

E

the element type of the collection on which to add the loneElement method

CTC

the "collection type constructor" for the collection on which to add the loneElement method

Source
LoneElement.scala
Linear Supertypes
AnyRef, Any
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Inherited
  1. LoneElementCollectionWrapper
  2. AnyRef
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  1. Public
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Instance Constructors

  1. new LoneElementCollectionWrapper(collection: CTC[E], collecting: Collecting[E, CTC[E]], prettifier: Prettifier, pos: Position)

    collection

    a collection to wrap in a LoneElementCollectionWrapper, which provides the loneElement method.

    collecting

    a typeclass that enables the loneElement syntax

Value Members

  1. def loneElement: E

    Returns the value contained in the wrapped collection, if it contains one and only one element, else throws TestFailedException with a detail message describing the problem.

    Returns the value contained in the wrapped collection, if it contains one and only one element, else throws TestFailedException with a detail message describing the problem.

    This method enables syntax such as the following:

    trav.loneElement should be > 9
     ^