minor #1410 Update testing.rst - preventing Fatal Error: Class...

minor #1410 Update testing.rst - preventing Fatal Error: Class 'Silex\WebTestCase' not found (Czarnodziej)

This PR was submitted for the master branch but it was merged into the 1.3 branch instead (closes #1410).

Discussion
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Update testing.rst - preventing Fatal Error: Class 'Silex\WebTestCase' not found

Taken from:
https://github.com/silexphp/Silex-Skeleton/blob/master/phpunit.xml.dist

Not adding bootstrap segment to phpunit.xml.dist causes Fatal Error: Class 'Silex\WebTestCase' not found

Commits
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ac35d9d1 Update testing.rst

doc/testing.rst

@@ -192,6 +192,7 @@ look like this:
              processIsolation="false"
              stopOnFailure="false"
              syntaxCheck="false"
+             bootstrap="vendor/autoload.php"
     >
         <testsuites>
             <testsuite name="YourApp Test Suite">