SNOW-2000709 add further integ/unit tests to guard the behaviors of no-auth

### Description
- Add more integ/unit tests to guard the behavior of no-auth
  - The goal is to avoid future changes accidentally and silently break the behavior of no-auth. (Eventually we want to have end-to-end tests to guard it when the Stored Procedure support is completed)

Author: sfc-gh-zyao

test/integ/test_connection.py

@@ -1575,6 +1575,23 @@ def test_is_valid(conn_cnx):
     assert conn.is_valid() is False
 
 
+@pytest.mark.skipolddriver
+def test_no_auth_connection_basic():
+    """Tests connection creation with AuthNoAuth."""
+    # AuthNoAuth does not exist in old drivers, so we import at test level to
+    # skip importing it for old driver tests.
+    from snowflake.connector.auth.no_auth import AuthNoAuth
+
+    no_auth = AuthNoAuth()
+
+    # Simulates how Snowpark server creates no-auth connection, such creation
+    # should succeed. Here we intentionally avoid using create_connection test
+    # utility. Because we want to validate that even with much information
+    # (like account, user etc.) missing, we should still be able to create a
+    # no-auth connection.
+    snowflake.connector.connect(auth_class=no_auth)
+
+
 @pytest.mark.skipolddriver
 def test_no_auth_connection_negative_case():
     # AuthNoAuth does not exist in old drivers, so we import at test level to
@@ -1583,10 +1600,15 @@ def test_no_auth_connection_negative_case():
 
     no_auth = AuthNoAuth()
 
-    # Create a no-auth connection in an invalid way.
-    # We do not fail connection establishment because there is no validated way
-    # to tell whether the no-auth is a valid use case or not. But it is
-    # effectively protected because invalid no-auth will fail to run any query.
+    # Create a no-auth connection in user code (and we create connection as we
+    # would for other tests, to provide all the needed information like
+    # account, user etc.). Such connection can be successfully created, but it
+    # is not fully functional because it lacks certain setup that is on the
+    # server side.
+    # We do not fail connection establishment in user code because there is no
+    # validated way to tell whether the no-auth is a valid use case or not. But
+    # it is effectively protected because invalid no-auth will fail to run any
+    # query.
     conn = create_connection("default", auth_class=no_auth)
 
     # Make sure we are indeed passing the no-auth configuration to the

test/unit/test_auth_no_auth.py

@@ -4,8 +4,13 @@
 
 from __future__ import annotations
 
+import unittest
+from unittest.mock import Mock
+
 import pytest
 
+import snowflake.connector
+
 
 @pytest.mark.skipolddriver
 def test_auth_no_auth():
@@ -38,3 +43,136 @@ def test_auth_no_auth():
     assert (
         reauth_response == expected_reauth_response
     ), f'reauthenticate(foo="bar") is expected to return {expected_reauth_response}, but returns {reauth_response}'
+
+
+@pytest.mark.skipolddriver
+def test_authenticate_for_no_auth():
+    from snowflake.connector.auth import Auth
+    from snowflake.connector.auth.no_auth import AuthNoAuth
+
+    rest = None
+    auth = Auth(rest)
+
+    # Verify that when using AuthNoAuth, we can successfully call authenticate
+    # even under these conditions
+    #   - None account is provided
+    #   - None user is provided
+    #   - restful client is not set up
+    auth.authenticate(AuthNoAuth(), account=None, user=None)
+
+
+class TestHeartbeatExecutionFlowForNoAuth(unittest.TestCase):
+    @pytest.mark.skipolddriver
+    def test_hearbeat_execution_flow_for_no_auth(self):
+        """Tests the heartbeat execution flow no-auth connections.
+
+        No-auth connection relies on these facts
+          - connection uses _heartbeat_tick method to perform heartbeat check
+          - _heartbeat_tick method calls connection._rest._heartbeat method to
+            send out the actual heartbeat request
+          - client_session_keep_alive_heartbeat_frequency (setter) calls
+            master_validity_in_seconds of the restful client to get the
+            reasonable value range.
+          - _validate_client_session_keep_alive_heartbeat_frequency calls
+            master_validity_in_seconds of the restful client to get the
+            reasonable value range.
+        And this test serves as a simple indicator to tell developers when a
+        code change breaks such assumptions.
+        """
+        # AuthNoAuth does not exist in old drivers, so we import at test level
+        # to skip importing it for old driver tests.
+        from snowflake.connector.auth.no_auth import AuthNoAuth
+
+        no_auth = AuthNoAuth()
+        conn = snowflake.connector.connect(auth_class=no_auth)
+        # Simulate how we inject special restful client for no-auth connection.
+        # And the tests verify that even with only the attributes listed below
+        # available in conn._rest, the tested heartbeat functionalities are
+        # still working as intended.
+        conn._rest = Mock(spec=["_heartbeat", "master_validity_in_seconds"])
+        conn._rest.master_validity_in_seconds = 100
+
+        breaking_change_error_message = """
+            Unexpected execution flow for heartbeat, this means potential
+            changes to heartbeat mechanism that will break no-auth connection
+            feature. Please contact the owner of AuthNoAuth before proceeding.
+            Details: {details}
+        """
+
+        # Check that _heartbeat_tick is working as intended.
+        try:
+            conn._heartbeat_tick()
+            conn._rest._heartbeat.assert_called_once()
+        except Exception as e:
+            raise AssertionError(breaking_change_error_message.format(details=str(e)))
+
+        # Check that client_session_keep_alive_heartbeat_frequency setter is
+        # working as intended with such a bare minimum set of interfaces
+        # exposed in conn._rest.
+        try:
+            conn.client_session_keep_alive_heartbeat_frequency = 123
+        except Exception as e:
+            raise AssertionError(breaking_change_error_message.format(details=str(e)))
+
+        # Check that _validate_client_session_keep_alive_heartbeat_frequency is
+        # working as intended with such a bare minimum set of interfaces
+        # exposed in conn._rest.
+        try:
+            conn._validate_client_session_keep_alive_heartbeat_frequency()
+        except Exception as e:
+            raise AssertionError(breaking_change_error_message.format(details=str(e)))
+
+        # Indirect way to check that
+        # client_session_keep_alive_heartbeat_frequency setter calls
+        # master_validity_in_seconds in conn._rest.
+        conn._rest = Mock(spec=["_heartbeat"])
+        missing_master_validity_in_seconds_message = (
+            "has no attribute 'master_validity_in_seconds'"
+        )
+        validity_dependency_change_template = (
+            "{method} no longer relies on rest.master_validity_in_seconds"
+        )
+        try:
+            # Verify that client_session_keep_alive_heartbeat_frequency setter
+            # fails when conn._rest.master_validity_in_seconds method is
+            # unavailable.
+            with self.assertRaises(AttributeError) as context:
+                conn.client_session_keep_alive_heartbeat_frequency = 123
+            self.assertIn(
+                missing_master_validity_in_seconds_message,
+                str(context.exception),
+            )
+        except Exception:
+            # This means there might be change breaking heartbeat mechanism for
+            # no-auth connections.
+            raise RuntimeError(
+                breaking_change_error_message.format(
+                    details=validity_dependency_change_template.format(
+                        method="client_session_keep_alive_heartbeat_frequency (setter)"
+                    )
+                )
+            )
+
+        # Likewise, this is an indirect way to check that
+        # _validate_client_session_keep_alive_heartbeat_frequency calls
+        # master_validity_in_seconds in conn._rest.
+        try:
+            # Verify that _validate_client_session_keep_alive_heartbeat_frequency
+            # fails when conn._rest.master_validity_in_seconds method is
+            # unavailable.
+            with self.assertRaises(AttributeError) as context:
+                conn._validate_client_session_keep_alive_heartbeat_frequency()
+            self.assertIn(
+                missing_master_validity_in_seconds_message,
+                str(context.exception),
+            )
+        except Exception:
+            # This means there might be change breaking heartbeat mechanism for
+            # no-auth connections.
+            raise RuntimeError(
+                breaking_change_error_message.format(
+                    details=validity_dependency_change_template.format(
+                        method="_validate_client_session_keep_alive_heartbeat_frequency"
+                    )
+                )
+            )