public function testValidHeader()
{
$dumper = new CombinedFileDumper($this->mockFilesystem("<?php\necho 'foo';\necho 'test';\n"), $this->mockLoader(), $this->getCacheDir());
$dumper->setHeader("<?php\necho 'foo';");
$dumper->dump(['test.php'], 'test.php');
}