Added unit test for Image element

Author: magneticflux-

src/test/groovy/com/github/magneticflux/rss/UrlUtils.groovy

@@ -0,0 +1,7 @@
+package com.github.magneticflux.rss
+
+class UrlUtils {
+	static URL testUrl() {
+		return new URL('http://www.example.com')
+	}
+}

src/test/groovy/com/github/magneticflux/rss/namespaces/standard/elements/ImageTest.groovy

@@ -0,0 +1,55 @@
+package com.github.magneticflux.rss.namespaces.standard.elements
+
+import com.github.magneticflux.rss.PersisterSpecification
+import spock.lang.Unroll
+
+import static com.github.magneticflux.rss.UrlUtils.testUrl
+
+class ImageTest extends PersisterSpecification {
+	@Unroll
+	def 'enclosure #object read/write'() {
+
+		expect: 'the output XML equals the given XML'
+		persister.write(object) == xml
+
+		and: 'the input object equals the given object'
+		persister.read(Image, xml) == object
+
+		where:
+		url       | title       | link      | description       | widthRaw | heightRaw | xml
+		testUrl() | 'testTitle' | testUrl() | 'testDescription' | '100'    | '100'     | """<image>
+                                                                                           |   <url>$url</url>
+                                                                                           |   <title>$title</title>
+                                                                                           |   <link>$link</link>
+                                                                                           |   <description>$description</description>
+                                                                                           |   <width>$widthRaw</width>
+                                                                                           |   <height>$heightRaw</height>
+                                                                                           |</image>""".stripMargin()
+
+		testUrl() | 'testTitle' | testUrl() | null              | '100'    | '100'     | """<image>
+                                                                                           |   <url>$url</url>
+                                                                                           |   <title>$title</title>
+                                                                                           |   <link>$link</link>
+                                                                                           |   <width>$widthRaw</width>
+                                                                                           |   <height>$heightRaw</height>
+                                                                                           |</image>""".stripMargin()
+
+		testUrl() | 'testTitle' | testUrl() | 'testDescription' | null     | '100'     | """<image>
+                                                                                           |   <url>$url</url>
+                                                                                           |   <title>$title</title>
+                                                                                           |   <link>$link</link>
+                                                                                           |   <description>$description</description>
+                                                                                           |   <height>$heightRaw</height>
+                                                                                           |</image>""".stripMargin()
+
+		testUrl() | 'testTitle' | testUrl() | 'testDescription' | '100'    | null      | """<image>
+                                                                                           |   <url>$url</url>
+                                                                                           |   <title>$title</title>
+                                                                                           |   <link>$link</link>
+                                                                                           |   <description>$description</description>
+                                                                                           |   <width>$widthRaw</width>
+                                                                                           |</image>""".stripMargin()
+
+		object = new Image(url, title, link, description, widthRaw, heightRaw)
+	}
+}