+ * @example $("input[@type='checkbox']").parent().is("form")
+ * @before <form><input type="checkbox" /></form>
+ * @result true
+ * @desc Returns true, because the parent of the input is a form element
+ *
+ * @example $("input[@type='checkbox']").parent().is("form")
+ * @before <form><p><input type="checkbox" /></p></form>
+ * @result false
+ * @desc Returns false, because the parent of the input is a p element
+ *
+ * @example $("form").is(null)
+ * @before <form></form>
+ * @result false
+ * @desc An invalid expression always returns false.
+ *
+ * @test ok( $('#form').is('form'), 'Check for element: A form must be a form' );
+ * @test ok( !$('#form').is('div'), 'Check for element: A form is not a div' );
+ * @test ok( $('#mark').is('.blog'), 'Check for class: Expected class "blog"' );
+ * @test ok( !$('#mark').is('.link'), 'Check for class: Did not expect class "link"' );
+ * @test ok( $('#simon').is('.blog.link'), 'Check for multiple classes: Expected classes "blog" and "link"' );
+ * @test ok( !$('#simon').is('.blogTest'), 'Check for multiple classes: Expected classes "blog" and "link", but not "blogTest"' );
+ * @test ok( $('#en').is('[@lang="en"]'), 'Check for attribute: Expected attribute lang to be "en"' );
+ * @test ok( !$('#en').is('[@lang="de"]'), 'Check for attribute: Expected attribute lang to be "en", not "de"' );
+ * @test ok( $('#text1').is('[@type="text"]'), 'Check for attribute: Expected attribute type to be "text"' );
+ * @test ok( !$('#text1').is('[@type="radio"]'), 'Check for attribute: Expected attribute type to be "text", not "radio"' );
+ * @test ok( $('#text2').is(':disabled'), 'Check for pseudoclass: Expected to be disabled' );
+ * @test ok( !$('#text1').is(':disabled'), 'Check for pseudoclass: Expected not disabled' );
+ * @test ok( $('#radio2').is(':checked'), 'Check for pseudoclass: Expected to be checked' );
+ * @test ok( !$('#radio1').is(':checked'), 'Check for pseudoclass: Expected not checked' );
+ * @test ok( $('#foo').is('[p]'), 'Check for child: Expected a child "p" element' );
+ * @test ok( !$('#foo').is('[ul]'), 'Check for child: Did not expect "ul" element' );
+ * @test ok( $('#foo').is('[p][a][code]'), 'Check for childs: Expected "p", "a" and "code" child elements' );
+ * @test ok( !$('#foo').is('[p][a][code][ol]'), 'Check for childs: Expected "p", "a" and "code" child elements, but no "ol"' );
+ * @test ok( !$('#foo').is(0), 'Expected false for an invalid expression - 0' );
+ * @test ok( !$('#foo').is(null), 'Expected false for an invalid expression - null' );
+ * @test ok( !$('#foo').is(''), 'Expected false for an invalid expression - ""' );
+ * @test ok( !$('#foo').is(undefined), 'Expected false for an invalid expression - undefined' );
+ *
+ * @name is