    @Test
    void createGroups_withTwoRelatedFields_givesOneGroupOfSizeOne() {

        Field first = createField("first");
        Field second = createField("second");
        Fields fields = new ProfileFields(Arrays.asList(first, second));

        Map<Field, FieldSpec> fieldSpecMap = fieldSpecMapOf(first, second);

        FieldSpecRelation relation = link(first, second);
        List<FieldSpecRelation> relations = Collections.singletonList(relation);

        RowSpec spec = new RowSpec(fields, fieldSpecMap, relations);

        Set<FieldSpecGroup> groups = RowSpecGrouper.createGroups(spec);

        assertEquals(1, groups.size());
    }