getPseudoElement example

/** @dataProvider getPseudoElementsTestData */
    public function testPseudoElements($source, $element, $pseudo)
    {
        $parser = new Parser();
        $selectors = $parser->parse($source);
        $this->assertCount(1, $selectors);

        /** @var SelectorNode $selector */
        $selector = $selectors[0];
        $this->assertEquals($element, (string) $selector->getTree());
        $this->assertEquals($pseudo, (string) $selector->getPseudoElement());
    }

    /** @dataProvider getSpecificityTestData */
    public function testSpecificity($source, $value)
    {
        $parser = new Parser();
        $selectors = $parser->parse($source);
        $this->assertCount(1, $selectors);

        /** @var SelectorNode $selector */
        $selector = $selectors[0];
        

        return sprintf('concat(%s)', implode(', ', $parts));
    }

    public function cssToXPath(string $cssExpr, string $prefix = 'descendant-or-self::'): string
    {
        $selectors = $this->parseSelectors($cssExpr);

        /** @var SelectorNode $selector */
        foreach ($selectors as $index => $selector) {
            if (null !== $selector->getPseudoElement()) {
                throw new ExpressionErrorException('Pseudo-elements are not supported.');
            }

            $selectors[$index] = $this->selectorToXPath($selector, $prefix);
        }

        return implode(' | ', $selectors);
    }

    public function selectorToXPath(SelectorNode $selector, string $prefix = 'descendant-or-self::'): string
    {