[test] Add a test case for yams_component_target predicate

test/test_mappers.py

@@ -36,6 +36,7 @@ from cubicweb_jsonschema.mappers import (
     JSONSchemaDeserializer,
     JSONSchemaSerializer,
     CompoundMapper,
+    yams_component_target,
     yams_match
 )
 
@@ -1666,6 +1667,32 @@ class PredicatesTC(CubicWebTC):
                                    target_types={'Bytes'}),
                          4)
 
+    def test_yams_component_target(self):
+        predicate = yams_component_target()
+        with self.admin_access.cnx() as cnx:
+            # 'thumbnail' is composite='subject'.
+            self.assertEqual(
+                predicate(None, cnx, rtype='thumbnail', role='subject',
+                          etype='Photo'),
+                1,
+            )
+            self.assertEqual(
+                predicate(None, cnx, rtype='thumbnail', role='object',
+                          etype='Thumbnail'),
+                0,
+            )
+            # 'topics' is not composite.
+            self.assertEqual(
+                predicate(None, cnx, rtype='topics', role='subject',
+                          etype='Book'),
+                0,
+            )
+            self.assertEqual(
+                predicate(None, cnx, rtype='topics', role='object',
+                          etype='Topic'),
+                0,
+            )
+
 
 if __name__ == '__main__':
     unittest.main()