test: fix test for designated import handlers

tests/test_app.py

@@ -1,5 +1,7 @@
 # -*- coding: utf-8; -*-
 
+from unittest.mock import patch
+
 from wuttjamaican.testing import ConfigTestCase
 
 from wuttasync import app as mod
@@ -16,6 +18,16 @@ class FromCsvToPoser(FromCsvToWutta):
     pass
 
 
+class FromFooToBaz1(ImportHandler):
+    source_key = "foo"
+    target_key = "baz"
+
+
+class FromFooToBaz2(ImportHandler):
+    source_key = "foo"
+    target_key = "baz"
+
+
 class TestWuttaSyncAppProvider(ConfigTestCase):
 
     def test_get_all_import_handlers(self):
@@ -100,6 +112,18 @@ class TestWuttaSyncAppProvider(ConfigTestCase):
             any([h.get_key() == "import.to_versions.from_wutta" for h in handlers])
         )
 
+        # nothing returned if multiple handlers found but none are designated
+        with patch.object(
+            self.app.providers["wuttasync"],
+            "get_all_import_handlers",
+            return_value=[FromFooToBaz1, FromFooToBaz2],
+        ):
+            handlers = self.app.get_designated_import_handlers()
+            baz_handlers = [
+                h for h in handlers if h.get_key() == "import.to_baz.from_foo"
+            ]
+            self.assertEqual(len(baz_handlers), 0)
+
     def test_get_import_handler(self):
 
         # make sure a basic fetch works