org.scalatest

EitherValues

trait EitherValues extends AnyRef

Trait that provides an implicit conversion that adds left.value and right.value 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.right.value should be > 9
either2.left.value should be ("Muchas problemas")

Or, using assertions instead of matcher expressions:

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

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

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

either.right.get should be > 9 // 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] = Left("Muchas problemas")

either should be ('right) // throws TestFailedException
either.right.get should be > 9

The EitherValues trait allows you to state that more concisely:

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

either.right.value should be > 9 // either.right.value throws TestFailedException

Source
EitherValues.scala
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Type Members

  1. class LeftValuable[L, R] extends AnyRef

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

  2. class RightValuable[L, R] extends AnyRef

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

Value Members

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

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

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  3. final def ##(): Int

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

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  8. implicit def convertLeftProjectionToValuable[L, R](leftProj: LeftProjection[L, R]): LeftValuable[L, R]

    Implicit conversion that adds a value method to LeftProjection.

  9. implicit def convertRightProjectionToValuable[L, R](rightProj: RightProjection[L, R]): RightValuable[L, R]

    Implicit conversion that adds a value method to RightProjection.

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

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  11. def equals(arg0: Any): Boolean

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  12. def finalize(): Unit

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

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

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  20. def toString(): String

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  21. final def wait(): Unit

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

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

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