public function testTimestampFromCache()
 {
     $writer = new AssetWriter(['js' => true, 'css' => false], TMP);
     $time = time();
     $writer->buildFilename($this->target);
     // delete the file so we know we hit the cache.
     unlink(TMP . AssetWriter::BUILD_TIME_FILE);
     $result = $writer->buildFilename($this->target);
     $this->assertEquals('test.v' . $time . '.js', $result);
 }