add some unittests for python Session

test arguments, deprecated as well as new mode arguments
test creating a session with a new xml file using __init__()
and begin(). Test raising exception when opening nonexistent
file without respective mode setting.

bindings/python/tests/test_session.py

@@ -10,12 +10,57 @@
 
 from unittest import TestCase, main
 
-from gnucash import Session
+from gnucash import (
+        Session,
+        SessionOpenMode
+)
+
+from gnucash.gnucash_core import GnuCashBackendException
 
 class TestSession(TestCase):
     def test_create_empty_session(self):
         self.ses = Session()
 
+    def test_session_deprecated_arguments(self):
+        """use deprecated arguments ignore_lock, is_new, force_new"""
+        self.ses = Session(ignore_lock=False, is_new=True, force_new=False)
+
+    def test_session_mode(self):
+        """use mode argument"""
+        self.ses = Session(mode=SessionOpenMode.SESSION_NORMAL_OPEN)
+
+    def test_session_with_new_file(self):
+        """create Session with new xml file"""
+        from tempfile import TemporaryDirectory
+        from urllib.parse import urlunparse
+        with TemporaryDirectory() as tempdir:
+            uri = urlunparse(("xml", tempdir, "tempfile", "", "", ""))
+            with Session(uri, SessionOpenMode.SESSION_NEW_STORE) as ses:
+                pass
+
+            # try to open nonexistent file without NEW mode - should raise Exception
+            uri = urlunparse(("xml", tempdir, "tempfile2", "", "", ""))
+            with Session() as ses:
+                with self.assertRaises(GnuCashBackendException):
+                    ses.begin(uri, mode=SessionOpenMode.SESSION_NORMAL_OPEN)
+
+            # try to open nonexistent file without NEW mode - should raise Exception
+            # use deprecated arg is_new
+            uri = urlunparse(("xml", tempdir, "tempfile2", "", "", ""))
+            with Session() as ses:
+                with self.assertRaises(GnuCashBackendException):
+                    ses.begin(uri, is_new=False)
+
+            uri = urlunparse(("xml", tempdir, "tempfile3", "", "", ""))
+            with Session() as ses:
+                ses.begin(uri, mode=SessionOpenMode.SESSION_NEW_STORE)
+
+            # test using deprecated args
+            uri = urlunparse(("xml", tempdir, "tempfile4", "", "", ""))
+            with Session() as ses:
+                ses.begin(uri, is_new=True)
+
+
     def test_app_utils_get_current_session(self):
         from gnucash import _sw_app_utils
         self.ses_instance = _sw_app_utils.gnc_get_current_session()