Documented the catchExceptions() method

Author: javiereguiluz

testing.rst

@@ -521,6 +521,19 @@ will no longer be followed::
 
     $client->followRedirects(false);
 
+Reporting Exceptions
+~~~~~~~~~~~~~~~~~~~~
+
+.. versionadded:: 3.4
+    The ``catchExceptions()`` method was introduced in Symfony 3.4.
+
+Debugging exceptions in functional tests may be difficult because by default
+they are caught and you need to look at the logs to see which exception was
+thrown. Disabling catching of exceptions in the test client allows the exception
+to be reported by PHPUnit::
+
+    $client->catchExceptions(false);
+
 .. index::
    single: Tests; Crawler