MINOR: add test for sqla compiler (#15275)

* add test for sqla compiler

ingestion/tests/unit/connections/test_test_connections.py

@@ -0,0 +1,53 @@
+from contextlib import contextmanager
+from unittest.mock import Mock
+
+import pytest
+from sqlalchemy import create_engine
+
+from metadata.ingestion.connections.test_connections import (
+    test_connection_engine_step as fn_test_connection_engine_step,  # renamed to avoid getting picked up as test by pytest
+)
+
+
+def assert_execute(engine, expected_query):
+    def inner(query, *_, **__):
+        assert str(query.compile(dialect=engine.dialect)) == expected_query
+
+    return inner
+
+
+def create_mock_connect(mock):
+    @contextmanager
+    def mock_connect(*_, **__):
+        yield mock
+
+    return mock_connect
+
+
+@pytest.fixture(autouse=True, scope="function")
+def bigquery(monkeypatch):
+    monkeypatch.setattr(
+        "sqlalchemy_bigquery._helpers.create_bigquery_client",
+        Mock(),
+    )
+
+
+@pytest.mark.parametrize(
+    "dialect,expected_test_fn",
+    (
+        [
+            ("sqlite", "SELECT 42"),
+            ("mysql", "SELECT 42"),
+            ("bigquery", "SELECT SESSION_USER()"),
+            # TODO this is skipped because installing ibm_db_sa requires going through hoops
+            # ("ibmi", "SELECT 42 FROM SYSIBM.SYSDUMMY1;"),
+        ]
+    ),
+)
+def test_test_connection_engine_step(dialect, expected_test_fn):
+    engine = create_engine(dialect + "://")
+    mock_connect = Mock()
+    mock_connect.execute = assert_execute(engine, expected_test_fn)
+    if dialect != "sqlite":
+        engine.connect = create_mock_connect(mock_connect)
+    fn_test_connection_engine_step(engine)