org.scalatest.enablers

Length

trait Length[T] extends AnyRef

Supertrait for Length typeclasses.

Trait Length is a typeclass trait for objects that can be queried for length. Objects of type T for which an implicit Length[T] is available can be used with the should have length syntax. In other words, this trait enables you to use the length checking syntax with arbitrary objects. As an example, consider java.net.DatagramPacket, which has a getLength method. By default, this can't be used with ScalaTest's have length syntax.

scala> import java.net.DatagramPacket
import java.net.DatagramPacket

scala> import org.scalatest.Matchers._
import org.scalatest.Matchers._

scala> val dp = new DatagramPacket(Array(0x0, 0x1, 0x2, 0x3), 4)
dp: java.net.DatagramPacket = java.net.DatagramPacket@54906181

scala> dp.getLength
res0: Int = 4

scala> dp should have length 4
:13: error: could not find implicit value for parameter ev: org.scalatest.matchers.ShouldMatchers.Extent[java.net.DatagramPacket]
         dp should have length 4
            ^

scala> implicit val lengthOfDatagramPacket =
    |   new Length[DatagramPacket] {
    |     def lengthOf(dp: DatagramPacket): Long = dp.getLength
    |   }
lengthOfDatagramPacket: java.lang.Object with org.scalatest.matchers.ShouldMatchers.Length[java.net.DatagramPacket] = $anon$1@550c6b37

scala> dp should have length 4

scala> dp should have length 3
org.scalatest.exceptions.TestFailedException:  java.net.DatagramPacket@54906181 had length 4, not length 3

Source
Length.scala
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Abstract Value Members

  1. abstract def lengthOf(obj: T): Long

    Returns the length of the passed object.

    Returns the length of the passed object.

    obj

    the object whose length to return

    returns

    the length of the passed object

Concrete Value Members

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

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