Size

Supertrait for Size type classes.

This traits enable you to use ScalaTest matchers' “have size” syntax to be used 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.awt.image.DataBufferByte
import java.awt.image.DataBufferByte

scala> import org.scalatest.matchers.ShouldMatchers._
import org.scalatest.matchers.ShouldMatchers._

scala> val db = new DataBufferByte(4)
db: java.awt.image.DataBufferByte = java.awt.image.DataBufferByte@33d5e94f

scala> db.getSize
res0: Int = 4

scala> db should have size 4
:17: error: could not find implicit value for parameter ev: org.scalatest.matchers.ShouldMatchers.Extent[java.awt.image.DataBufferByte]
              db should have size 4
                 ^
scala> implicit val sizeOfDataBufferByte =
     |   new Size[DataBufferByte] {
     |     def extentOf(db: DataBufferByte): Long = db.getSize
     |   }
sizeOfDataBufferByte: java.lang.Object with org.scalatest.matchers.ShouldMatchers.Size[java.awt.image.DataBufferByte] = $anon$1@4c69bdf8

scala> db should have size 4

scala> db should have size 3
org.scalatest.exceptions.TestFailedException:  java.awt.image.DataBufferByte@33d5e94f had size 4, not size 3