org.scalatest

LoneElement

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.

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))

Linear Supertypes
AnyRef, Any
Known Subclasses
LoneElement
Ordering
  1. Alphabetic
  2. By inheritance
Inherited
  1. LoneElement
  2. AnyRef
  3. Any
  1. Hide All
  2. Show all
Learn more about member selection
Visibility
  1. Public
  2. All

Type Members

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

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

  2. final class LoneElementJavaMapWrapper[K, V, JMAP[_, _] <: Map[_, _]] extends AnyRef

Value Members

  1. final def !=(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef

  2. final def !=(arg0: Any): Boolean

    Definition Classes
    Any

  3. final def ##(): Int

    Definition Classes
    AnyRef → Any

  4. final def ==(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef

  5. final def ==(arg0: Any): Boolean

    Definition Classes
    Any

  6. final def asInstanceOf[T0]: T0

    Definition Classes
    Any

  7. def clone(): AnyRef

    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws()

  8. implicit def convertJavaMapToCollectionLoneElementWrapper[K, V, JMAP[_, _] <: Map[_, _]](jmap: JMAP[K, V])(implicit collecting: Collecting[Entry[K, V], JMAP[K, V]]): LoneElementJavaMapWrapper[K, V, JMAP]

  9. implicit def convertToCollectionLoneElementWrapper[E, CTC[_]](collection: CTC[E])(implicit collecting: Collecting[E, CTC[E]]): LoneElementCollectionWrapper[E, CTC]

    Implicit conversion that adds a loneElement method to any collection type C for which an implicit Collection[C] is available.

    Implicit conversion that adds a loneElement method to any collection type C for which an implicit Collection[C] is available.

    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

    collection

    the collection on which to add the loneElement method

    collecting

    a typeclass that enables the loneElement syntax

  10. final def eq(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef

  11. def equals(arg0: Any): Boolean

    Definition Classes
    AnyRef → Any

  12. def finalize(): Unit

    Attributes
    protected[java.lang]
    Definition Classes
    AnyRef
    Annotations
    @throws()

  13. final def getClass(): Class[_]

    Definition Classes
    AnyRef → Any

  14. def hashCode(): Int

    Definition Classes
    AnyRef → Any

  15. final def isInstanceOf[T0]: Boolean

    Definition Classes
    Any

  16. final def ne(arg0: AnyRef): Boolean

    Definition Classes
    AnyRef

  17. final def notify(): Unit

    Definition Classes
    AnyRef

  18. final def notifyAll(): Unit

    Definition Classes
    AnyRef

  19. final def synchronized[T0](arg0: ⇒ T0): T0

    Definition Classes
    AnyRef

  20. def toString(): String

    Definition Classes
    AnyRef → Any

  21. final def wait(): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws()

  22. final def wait(arg0: Long, arg1: Int): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws()

  23. final def wait(arg0: Long): Unit

    Definition Classes
    AnyRef
    Annotations
    @throws()

Inherited from AnyRef

Inherited from Any

Ungrouped