Fix filter_box migration PR #6523 (#7066)

* Fix filter_box migration PR #6523

* Fix druid-related bug

(cherry picked from commit b210742ad2)

tests/migration_tests.py

@@ -0,0 +1,42 @@
+# Licensed to the Apache Software Foundation (ASF) under one
+# or more contributor license agreements.  See the NOTICE file
+# distributed with this work for additional information
+# regarding copyright ownership.  The ASF licenses this file
+# to you under the Apache License, Version 2.0 (the
+# "License"); you may not use this file except in compliance
+# with the License.  You may obtain a copy of the License at
+#
+#   http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing,
+# software distributed under the License is distributed on an
+# "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
+# KIND, either express or implied.  See the License for the
+# specific language governing permissions and limitations
+# under the License.
+import json
+
+from superset.migrations.versions.fb13d49b72f9_better_filters import (
+    Slice, upgrade_slice,
+)
+from .base_tests import SupersetTestCase
+
+
+class MigrationTestCase(SupersetTestCase):
+
+    def test_upgrade_slice(self):
+        slc = Slice(
+            slice_name='FOO',
+            viz_type='filter_box',
+            params=json.dumps(dict(
+                metric='foo',
+                groupby=['bar'],
+            )),
+        )
+        upgrade_slice(slc)
+        params = json.loads(slc.params)
+        self.assertNotIn('metric', params)
+        self.assertIn('filter_configs', params)
+
+        cfg = params['filter_configs'][0]
+        self.assertEquals(cfg.get('metric'), 'foo')