[ErrorHandler][FrameworkBundle] better error messages in failing tests

[guillbdx]

Q	A
Branch?	master for features
Bug fix?	no
New feature?	yes
Deprecations?	no
Tickets	Fix #32752
License	MIT
Doc PR

Purpose of this PR is to enhance tests by giving a way to report an exception that occured during the processing of the request.

The ErrorHandler will add an X-Debug-Exception, and the assertThat() method of WebTestCase will throw an exception if this header exists and status code is 5xx.

In practice, this adds the "Caused by" section in this example:

Time: 374 ms, Memory: 20.00 MB

There was 1 failure:

1) App\Tests\Controller\HomeControllerTest::testC
Failed asserting that the Response has header "Content-Type" with value "application/json".

/srv/symfony/src/Symfony/Bundle/FrameworkBundle/Test/BrowserKitAssertionsTrait.php:132
/srv/symfony/src/Symfony/Bundle/FrameworkBundle/Test/BrowserKitAssertionsTrait.php:66
/srv/blog/tests/Controller/HomeControllerTest.php:29

Caused by
Exception: This a test exception. in /the/file.php:139
Stack trace:
[...]

[nicolas-grekas]

Cool! No more blind errors when using this testing API \o/

[yceruto]

I added some comments, thank you!

[fabpot]

Thank you @guillbdx.

[sstok]

Nice! This was the one thing missing from the new testing assertions. Thanks for working on this.

[eng1neer]

I'm getting an nginx error caused by a too large X-Debug-Exception header (upstream sent too big header while reading response header from upstream). This happens with a moderately large exception text (few kilobytes) and default nginx fastcgi buffer size settings. Is there any way to disable the X-Debug-Exception header population without disabling Symfony's debug mode altogether?

[derrabus]

Hello @eng1neer and thank you for reaching out.

This tracker is meant for tracking bugs and feature requests. If you are looking for support, you'll get faster responses by using one of our official support channels:

• StackOverflow: https://stackoverflow.com/questions/tagged/symfony
• Slack: https://symfony.com/slack

See https://symfony.com/support for more support options.

[eng1neer]

Hey, @derrabus thanks for taking the time to flag my message as off-topic.

I would argue that this is actually a bug. Stuffing data of an arbitrary length into HTTP headers is a bad idea. Most of the web servers impose a limit on the amount of data that can be transmitted in HTTP headers and this limit is not too big (4-8KB for Apache or Nginx). You can easily exceed it with a few kilobytes of text in the exception message which leads to an unexpected error page generated by the webserver.

There should be other, more appropriate ways to pass exception information in tests that will not intervene with the usual development workflow.

[derrabus]

@eng1neer All right then, please file a bug report.