Configures the mock implementation of $exceptionHandler to rethrow or to log errors passed into the $exceptionHandler.
$exceptionHandler
mode(mode);
Sets the logging mode.
Mode of operation, defaults to rethrow.
rethrow
means that there is a bug in the application or test, so this mock will make these tests fail.
log
mode stores an array of errors in `$exceptionHandler.errors`, to allow later assertion of them. See assertEmpty() and reset()