StreamlinedXmlEquality

Trait providing an implicit Equality[T] for subtypes of scala.xml.NodeSeq that before testing for equality, will normalize left and right sides by removing empty XML text nodes and trimming non-empty text nodes.

Here's an example of some unnormalized XML:

<summer>
 <day></day>
 <night>
   with lots of stars
 </night>
</summer>

Prior to testing it for equality, the implicit Equality[T] provided by this trait would transform the above XML to:

<summer><day></day><night>with lots of stars</night></summer>

The goal of this trait is to provide an implicit Equality for XML that makes it easier to write tests involving XML. White space is significant in XML, and is taken into account by the default equality for XML, accessed by invoking the == method on an XML NodeSeq. Here's an example:

scala> val xmlElem = <summer><day></day><night>with lots of stars</night></summer>
xmlElem: scala.xml.Elem = <summer><day></day><night>with lots of stars</night></summer>

scala> import org.scalatest.Assertions._
import org.scalatest.Assertions._

scala> assert(xmlElem === <summer>
    |   <day></day>
    |     <night>
    |       with lots of stars
    |     </night>
    |   </summer>)
org.scalatest.exceptions.TestFailedException: <summer><day></day><night>with lots of stars</night></summer> did not equal <summer>
 <day></day>
   <night>
     with lots of stars
   </night>
 </summer>
 at org.scalatest.Assertions$class.newAssertionFailedException(Assertions.scala:500)
 at org.scalatest.Assertions$.newAssertionFailedException(Assertions.scala:1538)
 at org.scalatest.Assertions$AssertionsHelper.macroAssert(Assertions.scala:466)
 ... 53 elided

The above assertion fails because of whitespace differences in the XML. When such whitespace differences are unimportant to the actual application, it can make it easier to write readable test code if you can compare XML for equality without taking into account empty text nodes, or leading and trailing whitespace in nonempty text nodes. This trait provides an Equality[T] instance that does just that:

scala> import org.scalatest.StreamlinedXmlEquality._
import org.scalatest.StreamlinedXmlEquality._

scala> assert(xmlElem === <summer>
    |   <day></day>
    |   <night>
    |     with lots of stars
    |   </night>
    | </summer>)