LoneElement

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))

Source: LoneElement.scala

Linear Supertypes

AnyRef, Any

Known Subclasses

LoneElement

Type Members

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

Wrapper class that adds a loneElement method to Java Map for which an implicit Collecting[org.scalatest.Entry, java.util.Map] is available.
Wrapper class that adds a loneElement method to Java Map for which an implicit Collecting[org.scalatest.Entry, java.util.Map] is available.
Through the implicit conversion provided by trait LoneElement, this class allows you to make statements like:
```
jmap.loneElement.getKey should be > 9
```
K
the element type of the Java Map key on which to add the loneElement method
V
the element type of the Java Map value on which to add the loneElement method
JMAP
the "Java Map type constructor" for the collection on which to add the loneElement method
final class LoneElementMapWrapper[K, V, MAP[k, v] <: GenMap[k, v]] extends AnyRef

Wrapper class that adds a loneElement method to Map for which an implicit Collecting[(K, V), scala.collection.GenTraversable[(K, V)]] is available.
Wrapper class that adds a loneElement method to Map for which an implicit Collecting[(K, V), scala.collection.GenTraversable[(K, V)]] is available.
Through the implicit conversion provided by trait LoneElement, this class allows you to make statements like:
```
map.loneElement._1 should be > 9
```
K
the element type of the Map key on which to add the loneElement method
V
the element type of the Map value on which to add the loneElement method
MAP
the "Map type constructor" for the collection on which to add the loneElement method
final class LoneElementStringWrapper extends AnyRef

Wrapper class that adds a loneElement method to String for which an implicit Collecting[C] is available.
Wrapper class that adds a loneElement method to String for which an implicit Collecting[C] is available.
Through the implicit conversion provided by trait LoneElement, this class allows you to make statements like:
```
"9".loneElement should be ('9')
```

Value Members

final def !=(arg0: Any): Boolean

Definition Classes
AnyRef → Any
final def ##(): Int

Definition Classes
AnyRef → Any
final def ==(arg0: Any): Boolean

Definition Classes
AnyRef → Any
final def asInstanceOf[T0]: T0

Definition Classes
Any
def clone(): AnyRef

Attributes
protected[java.lang]
Definition Classes
AnyRef
Annotations
@throws( ... )
implicit def convertJavaMapToCollectionLoneElementWrapper[K, V, JMAP[_, _] <: Map[_, _]](jmap: JMAP[K, V])(implicit collecting: Collecting[Entry[K, V], JMAP[K, V]], prettifier: Prettifier, pos: Position): LoneElementJavaMapWrapper[K, V, JMAP]
implicit def convertMapToCollectionLoneElementWrapper[K, V, MAP[k, v] <: GenMap[k, v]](map: MAP[K, V])(implicit collecting: Collecting[(K, V), GenTraversable[(K, V)]], prettifier: Prettifier, pos: Position): LoneElementMapWrapper[K, V, MAP]
implicit def convertToCollectionLoneElementWrapper[E, CTC[_]](collection: CTC[E])(implicit collecting: Collecting[E, CTC[E]], prettifier: Prettifier, pos: Position): LoneElementCollectionWrapper[E, CTC]

Implicit conversion that adds a loneElement method to any collection type C for which an implicit Collecting[C] is available.
Implicit conversion that adds a loneElement method to any collection type C for which an implicit Collecting[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
implicit def convertToStringLoneElementWrapper(s: String)(implicit prettifier: Prettifier, pos: Position): LoneElementStringWrapper

Implicit conversion that adds a loneElement method to String for which an implicit Collecting[C] is available.
Implicit conversion that adds a loneElement method to String for which an implicit Collecting[C] is available.
s
the String to wrap
final def eq(arg0: AnyRef): Boolean

Definition Classes
AnyRef
def equals(arg0: Any): Boolean

Definition Classes
AnyRef → Any
def finalize(): Unit

Attributes
protected[java.lang]
Definition Classes
AnyRef
Annotations
@throws( classOf[java.lang.Throwable] )
final def getClass(): Class[_]

Definition Classes
AnyRef → Any
def hashCode(): Int

Definition Classes
AnyRef → Any
final def isInstanceOf[T0]: Boolean

Definition Classes
Any
final def ne(arg0: AnyRef): Boolean

Definition Classes
AnyRef
final def notify(): Unit

Definition Classes
AnyRef
final def notifyAll(): Unit

Definition Classes
AnyRef
final def synchronized[T0](arg0: ⇒ T0): T0

Definition Classes
AnyRef
def toString(): String

Definition Classes
AnyRef → Any
final def wait(): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )
final def wait(arg0: Long, arg1: Int): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )
final def wait(arg0: Long): Unit

Definition Classes
AnyRef
Annotations
@throws( ... )

Related Docs: object LoneElement | package scalatest

trait LoneElement extends AnyRef

Type Members

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

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

final class LoneElementMapWrapper[K, V, MAP[k, v] <: GenMap[k, v]] extends AnyRef

final class LoneElementStringWrapper extends AnyRef

Value Members

final def !=(arg0: Any): Boolean

final def ##(): Int

final def ==(arg0: Any): Boolean

final def asInstanceOf[T0]: T0

def clone(): AnyRef

implicit def convertJavaMapToCollectionLoneElementWrapper[K, V, JMAP[_, _] <: Map[_, _]](jmap: JMAP[K, V])(implicit collecting: Collecting[Entry[K, V], JMAP[K, V]], prettifier: Prettifier, pos: Position): LoneElementJavaMapWrapper[K, V, JMAP]

implicit def convertMapToCollectionLoneElementWrapper[K, V, MAP[k, v] <: GenMap[k, v]](map: MAP[K, V])(implicit collecting: Collecting[(K, V), GenTraversable[(K, V)]], prettifier: Prettifier, pos: Position): LoneElementMapWrapper[K, V, MAP]

implicit def convertToCollectionLoneElementWrapper[E, CTC[_]](collection: CTC[E])(implicit collecting: Collecting[E, CTC[E]], prettifier: Prettifier, pos: Position): LoneElementCollectionWrapper[E, CTC]

implicit def convertToStringLoneElementWrapper(s: String)(implicit prettifier: Prettifier, pos: Position): LoneElementStringWrapper

final def eq(arg0: AnyRef): Boolean

def equals(arg0: Any): Boolean

def finalize(): Unit

final def getClass(): Class[_]

def hashCode(): Int

final def isInstanceOf[T0]: Boolean

final def ne(arg0: AnyRef): Boolean

final def notify(): Unit

final def notifyAll(): Unit

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

def toString(): String

final def wait(): Unit

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

final def wait(arg0: Long): Unit

Inherited from AnyRef

Inherited from Any

Ungrouped