cats.scalatest.EitherValues.scala Maven / Gradle / Ivy
package cats.scalatest
import org.scalatest.exceptions.{StackDepthException, TestFailedException}
import org.scalactic.source
import scala.util.{Either, Left, Right}
trait EitherValues {
import scala.language.implicitConversions
/**
* Implicit conversion that adds a `value` method to `scala.util.Either`
*
* @param either the `scala.util.Either` on which to add the `value` method
*/
implicit def convertEitherToEitherable[E, T](either: E Either T)(implicit pos: source.Position): Eitherable[E, T] =
new Eitherable(either, pos)
/**
* Container class for matching success
* type stuff in `scala.util.Either` containers,
* similar to `org.scalatest.OptionValues.Valuable`
*
* Meant to allow you to make statements like:
*
*
* result.value should be > 15
*
*
* Where it only matches if result is `Valid` and is also greater than 15.
*
* Otherwise your test will fail, indicating that it was left instead of right
*
* @param either A `scala.util.Either` object to try converting to a `Eitherable`
*
* @see org.scalatest.OptionValues.Valuable
*/
final class Eitherable[E, T](either: E Either T, pos: source.Position) {
/**
* Extract the `Right` from the Either. If the value is not a right the test will fail.
*/
def value: T =
either match {
case Right(right) => right
case Left(left) =>
throw new TestFailedException(
(_: StackDepthException) => Some(s"'$left' is a Left, expected a Right."),
None,
pos
)
}
/**
* Use .leftValue on an Either to extract the left side. Like .value, but for the left.
* If the value is a right, the test will fail.
*/
def leftValue: E =
either match {
case Right(right) =>
throw new TestFailedException(
(_: StackDepthException) => Some(s"'$right' is a Right, expected a Left."),
None,
pos
)
case Left(left) => left
}
}
}
/**
*
* Companion object for easy importing – rather than mixing in – to allow `EitherValues` operations.
*
* This will permit you to invoke a `value` method on an instance of a `scala.util.Either`,
* which attempts to unwrap the `Valid`.
*
* Similar to `org.scalatest.OptionValues.Valuable`
*
* Meant to allow you to make statements like:
*
*
* result.value should be > 15
*
*
* Where it only matches if result is both an `Either.Vaild` and has a value > 15.
*
* Otherwise your test will fail, indicating that it was an Invalid instead of Valid
*
* @see EitherValues.EitherValuable
*/
object EitherValues extends EitherValues