public function testPrependLine() { $prepend = vfsStream::newFile('prepend.txt', 0777); $this->root->addChild($prepend); $prepend->setContent('PHPUNIT'); $file = new File($prepend->url()); $file->prependLine('PREPENDED'); $this->assertEquals('PREPENDED' . PHP_EOL . 'PHPUNIT', file_get_contents($prepend->url())); }