Testing CSV output in Drupal 8 with BrowserTestBase

Basically, the easiest way to validate and parse CSV in PHP is with the built in fgetcsv function.

So how do you go about using that inside a functional test - in that instance we're not dealing with a file so its not your ordinary approach for fgetcsv.

The answer is to create a stream wrapper in memory, and use fgetcsv on that.

The code looks something like this:

    $response = $this->getSession()
      ->getDriver()
      ->getContent();
    // Put contents into a memory stream and use fgetcsv to parse.
    $stream = fopen('php://memory', 'r+');
    fwrite($stream, $response);
    rewind($stream);
    $records = [];
    // Get the header row.
    $header = fgetcsv($stream);
    while ($row = fgetcsv($stream)) {
      $records[] = $row;
    }
    fclose($stream);

There you have it, you now have the header in $header and the rows in $rows and can do any manner of asserts that you need to validate the CSV generation works as expected.