Complete the test coverage of check_and_get_filename

Co-authored-by: Mohammed Almakki <mohammed.almakki@stfc.ac.uk>
Co-authored-by: Despina Ioannide <despina.ioannide@stfc.ac.uk>

Author: 3 people

qt/python/mantidqtinterfaces/test/Muon/grouping_tab/grouping_tab_presenter_test.py

@@ -4,6 +4,7 @@
 #   NScD Oak Ridge National Laboratory, European Spallation Source,
 #   Institut Laue - Langevin & CSNS, Institute of High Energy Physics, CAS
 # SPDX - License - Identifier: GPL - 3.0 +
+import os
 import unittest
 from unittest import mock
 from mantidqt.utils.qt.testing import start_qapplication
@@ -393,11 +394,40 @@ def test_periods_button_data_missing_added_successfully(self):
         self.assertEqual(1, self.presenter.period_info_widget.show.call_count)
 
     def test_check_and_get_filename_empty_filename(self):
-        # self.view.show_question_dialog = mock.MagicMock(return_value=True)
         filename = self.presenter._check_and_get_filename("")
-
         self.assertEqual(filename, "")
 
+    def test_check_and_get_filename_with_xml_extension(self):
+        expected_filename = "file.xml"
+        filename = self.presenter._check_and_get_filename(expected_filename)
+        self.assertEqual(filename, expected_filename)
+
+    def _run_test_check_and_get_filename_without_xml_extension(
+        self,
+        expected_filename,
+        given_filename,
+        isfile=True,
+        return_val=True,
+    ):
+        # Pretend file already exists.
+        os.path.isfile = mock.MagicMock(return_value=isfile)
+        # User selects "yes" to replace existing file
+        self.view.show_question_dialog = mock.MagicMock(return_value=return_val)
+
+        filename = self.presenter._check_and_get_filename(given_filename)
+        self.assertEqual(filename, expected_filename)
+
+    def test_check_and_get_filename_without_xml_extension_if_xml_file_exists(self):
+        self._run_test_check_and_get_filename_without_xml_extension("file.xml", "file.txt")
+
+    def test_check_and_get_filename_without_xml_extension_if_xml_file_exists_no_overwrite(
+        self,
+    ):
+        self._run_test_check_and_get_filename_without_xml_extension("", "file.txt")
+
+    def test_check_and_get_filename_without_xml_extension_if_xml_file_not_exists(self):
+        self._run_test_check_and_get_filename_without_xml_extension("file.xml", "file.txt", isfile=False, return_val=False)
+
 
 if __name__ == "__main__":
     unittest.main(buffer=False, verbosity=2)