When running phpunit with a specific filter - I get an error. 

./vendor/bin/phpunit --filter=analyse_res

Moodle 3.4dev (Build: 20170817), 27466d7548de99cbb050027acc3e809ce49ad2e9
Php: 7.0.19.1.2, mysqli: 5.5.55-0ubuntu0.14.04.1, OS: Linux 3.19.0-32-generic x86_64
PHPUnit 5.5.7 by Sebastian Bergmann and contributors.

.........E...... 16 / 16 (100%)

Time: 1.11 seconds, Memory: 148.00MB

There was 1 error:

1) qtype_missing_test::test_can_analyse_responses
Error: Class 'qtype_missingtype' not found

This means some code is using a class without requiring it.