assertXPath

gistfile1.txt

    /**
     * Assert that a XPath matches on a DomNode
     *
     * Uses the XPath Method boolean() to see if a node test evaluates to true
     * It's true if one of the follow conditions is met:
     *
     *  - a number is true if and only if it is neither positive or negative zero nor NaN
     *  - a node-set is true if and only if it is non-empty
     *  - a string is true if and only if its length is non-zero
     *  - an object of a type other than the four basic types is converted to a
     *    boolean in a way that is dependent on that type
     *
     * @see http://www.w3.org/TR/xpath/#section-Boolean-Functions
     *
     * @param string $xpath
     */
    public static function assertXPath($xpathQuery, DOMDocument $doc, $message = '') {
        $xpath = new \DOMXPath($doc);
        self::assertTrue(
            $xpath->evaluate("boolean($xpathQuery)"), 
            'Failed asserting that XPath expression: "' . $xpathQuery . '" evaluates to true. ' . $message
        );
    }