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/pinot_tests.py

@@ -0,0 +1,33 @@
+# 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.pinot import PinotEngineSpec
+from tests.db_engine_specs.base_tests import DbEngineSpecTestCase
+
+
+class PinotTestCase(DbEngineSpecTestCase):
+    """ Tests pertaining to our Pinot database support """
+
+    def test_pinot_time_expression_sec_one_1m_grain(self):
+        col = column("tstamp")
+        expr = PinotEngineSpec.get_timestamp_expr(col, "epoch_s", "P1M")
+        result = str(expr.compile())
+        self.assertEqual(
+            result,
+            'DATETIMECONVERT(tstamp, "1:SECONDS:EPOCH", "1:SECONDS:EPOCH", "1:MONTHS")',
+        )  # noqa