Split up tests/db_engine_test.py (#8449)

* Split up db_engine_specs_test.py into a number of targeted files

* Remove db_engine_specs_test.py

* isort

tests/db_engine_specs/bigquery_tests.py

@@ -0,0 +1,39 @@
+# 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.
+from sqlalchemy import column
+
+from superset.db_engine_specs.bigquery import BigQueryEngineSpec
+from tests.db_engine_specs.base_tests import DbEngineSpecTestCase
+
+
+class BigQueryTestCase(DbEngineSpecTestCase):
+    def test_bigquery_sqla_column_label(self):
+        label = BigQueryEngineSpec.make_label_compatible(column("Col").name)
+        label_expected = "Col"
+        self.assertEqual(label, label_expected)
+
+        label = BigQueryEngineSpec.make_label_compatible(column("SUM(x)").name)
+        label_expected = "SUM_x__5f110"
+        self.assertEqual(label, label_expected)
+
+        label = BigQueryEngineSpec.make_label_compatible(column("SUM[x]").name)
+        label_expected = "SUM_x__7ebe1"
+        self.assertEqual(label, label_expected)
+
+        label = BigQueryEngineSpec.make_label_compatible(column("12345_col").name)
+        label_expected = "_12345_col_8d390"
+        self.assertEqual(label, label_expected)