Relation support for multi-charm VNFs

Adds support for establishing relations between charms

Signed-off-by: Adam Israel <adam.israel@canonical.com>
Change-Id: I9a0b7725013e06635875cd824e219ab6a023efb3
diff --git a/tests/charms/layers/native-ci/reactive/native-ci.py b/tests/charms/layers/native-ci/reactive/native-ci.py
index 17bf5f4..9e5fe67 100644
--- a/tests/charms/layers/native-ci/reactive/native-ci.py
+++ b/tests/charms/layers/native-ci/reactive/native-ci.py
@@ -42,3 +42,21 @@
         action_set({'output': intval})
     finally:
         clear_flag('actions.testint')
+
+
+@when('db.joined')
+def provides_db(db):
+    """Simulate providing database credentials."""
+    db.configure(
+        database="mydb",
+        user="myuser",
+        password="mypassword",
+        host="myhost",
+        slave="myslave",
+    )
+
+
+@when('db.available')
+def requires_db(db):
+    """Simulate receiving database credentials."""
+    pass