add tests for the learning_units views
add tests for the learning_units views

fix #2168

uclouvain/OSIS-Louvain,uclouvain/osis_louvain,uclouvain/osis,uclouvain/osis,uclouvain/osis_louvain,uclouvain/osis_louvain,uclouvain/osis,uclouvain/OSIS-Louvain,uclouvain/OSIS-Louvain,uclouvain/osis