scalatestCoreDotty/org.scalatest/EitherValues

EitherValues

trait EitherValues extends Serializable

Trait that provides an implicit conversion that adds value (when you expect a Right) and left.value (when you expect a Left) methods to Either, which will return the selected value of the Either if defined, or throw TestFailedException if not.

This construct allows you to express in one statement that an Either should be left or right and that its value should meet some expectation. Here's are some examples:

either1.value should be > 9
either2.left.value should be ("Muchos problemas")

Or, using assertions instead of matcher expressions:

assert(either1.value > 9)
assert(either2.left.value === "Muchos problemas")

Were you to simply invoke left.get on the Either, if the Either wasn't defined as expected (e.g., it was a Right when you expected a Left), it would throw a NoSuchElementException:

val either: Either[String, Int] = Right(9)

either.left.get should be > "Muchos problemas" // either.right.get throws NoSuchElementException

The NoSuchElementException would cause the test to fail, but without providing a stack depth pointing to the failing line of test code. This stack depth, provided by TestFailedException (and a few other ScalaTest exceptions), makes it quicker for users to navigate to the cause of the failure. Without EitherValues, to get a stack depth exception you would need to make two statements, like this:

val either: Either[String, Int] = Right(9)

either should be ('left) // throws TestFailedException
either.left.get should be > "Muchos problemas"

The EitherValues trait allows you to state that more concisely:

val either: Either[String, Int] = Left("Muchas problemas")

either.left.value should be > 9 // either.left.value throws TestFailedException
Companion:
object
trait Serializable
class Object
trait Matchable
class Any
object EitherValues.type

Type members

Classlikes

class EitherValuable[L, R](either: Either[L, R], pos: Position) extends Serializable

Wrapper class that adds a value method to Either, allowing you to make statements to inspect the value if a Right, like:

Wrapper class that adds a value method to Either, allowing you to make statements to inspect the value if a Right, like:

either.value should be > 9
Value parameters:
either

An Either to convert to EitherValuable, which provides the value method.

class LeftValuable[L, R](leftProj: LeftProjection[L, R], pos: Position) extends Serializable

Wrapper class that adds a value method to LeftProjection, allowing you to make statements like:

Wrapper class that adds a value method to LeftProjection, allowing you to make statements like:

either.left.value should be > 9
Value parameters:
leftProj

A LeftProjection to convert to LeftValuable, which provides the value method.

class RightValuable[L, R](rightProj: RightProjection[L, R], pos: Position) extends Serializable

Wrapper class that adds a value method to RightProjection, allowing you to make statements like:

Wrapper class that adds a value method to RightProjection, allowing you to make statements like:

either.right.value should be > 9
Value parameters:
rightProj

A RightProjection to convert to RightValuable, which provides the value method.

Implicits

Implicits

implicit def convertEitherToValuable[L, R](either: Either[L, R])(implicit pos: Position): EitherValuable[L, R]

Implicit conversion that adds a value method to Either. This method is right biased and is the equivalent of calling either.right.value.

Implicit conversion that adds a value method to Either. This method is right biased and is the equivalent of calling either.right.value.

Value parameters:
either

the Either on which to add the value method

implicit def convertLeftProjectionToValuable[L, R](leftProj: LeftProjection[L, R])(implicit pos: Position): LeftValuable[L, R]

Implicit conversion that adds a value method to LeftProjection.

Implicit conversion that adds a value method to LeftProjection.

Value parameters:
leftProj

the LeftProjection on which to add the value method

Deprecated implicits

@deprecated("The .right.value syntax on Either has been deprecated and will be removed in a future version of ScalaTest. Please use .value instead.")
implicit def convertRightProjectionToValuable[L, R](rightProj: RightProjection[L, R])(implicit pos: Position): RightValuable[L, R]

Implicit conversion that adds a value method to RightProjection.

Implicit conversion that adds a value method to RightProjection.

Value parameters:
rightProj

the RightProjection on which to add the value method

Deprecated