added test for piccolo migrations check

Author: dantownsend

piccolo/apps/migrations/commands/base.py

@@ -6,7 +6,12 @@
 import sys
 import typing as t
 
-from piccolo.conf.apps import AppConfig, MigrationModule, PiccoloAppModule
+from piccolo.conf.apps import (
+    AppConfig,
+    MigrationModule,
+    PiccoloAppModule,
+    AppRegistry,
+)
 from piccolo.apps.migrations.auto.migration_manager import MigrationManager
 from piccolo.apps.migrations.auto.diffable_table import DiffableTable
 from piccolo.apps.migrations.auto.schema_snapshot import SchemaSnapshot
@@ -57,19 +62,22 @@ def _import_app_modules(
 
         return config_modules
 
-    def get_app_modules(self) -> t.List[PiccoloAppModule]:
-        """
-        Returns the piccolo_app.py modules for each registered Piccolo app.
-        """
+    def get_app_registry(self) -> AppRegistry:
         try:
             from piccolo_conf import APP_REGISTRY
         except ImportError:
             raise Exception(
                 "Unable to import APP_REGISTRY from piccolo_conf - make sure "
                 "it's in your path."
             )
+        return APP_REGISTRY
 
-        app_modules = self._import_app_modules(APP_REGISTRY.apps)
+    def get_app_modules(self) -> t.List[PiccoloAppModule]:
+        """
+        Returns the piccolo_app.py modules for each registered Piccolo app.
+        """
+        app_registry = self.get_app_registry()
+        app_modules = self._import_app_modules(app_registry.apps)
 
         # Now deduplicate any dependencies
         app_modules = self._deduplicate(app_modules)

piccolo/apps/migrations/commands/check.py

@@ -1,4 +1,4 @@
-from .base import BaseMigrationManager
+from piccolo.apps.migrations.commands.base import BaseMigrationManager
 from piccolo.apps.migrations.tables import Migration
 from piccolo.utils.printing import get_fixed_length_string
 

tests/apps/migrations/commands/test_check.py

@@ -0,0 +1,18 @@
+from unittest import TestCase
+from unittest.mock import patch, MagicMock
+
+from piccolo.conf.apps import AppRegistry
+from piccolo.apps.migrations.commands.check import check, CheckMigrationManager
+
+
+class TestCheckMigrationCommand(TestCase):
+    @patch.object(
+        CheckMigrationManager, "get_app_registry",
+    )
+    def test_check_migrations(self, get_app_registry: MagicMock):
+        get_app_registry.return_value = AppRegistry(
+            apps=["piccolo.apps.user.piccolo_app"]
+        )
+
+        # Make sure it runs without raising an exception:
+        check()