Add a unit test to verify that has_valid_headers() succeeds for an empty file. This allows removing test_fileoutput_has_valid_headers.py which is now completley redundant. (#981)

Author: cianc

tests/output_methods/test_file.py

@@ -70,6 +70,13 @@ def test_has_valid_headers_success(self):
 
         self.assertTrue(file_output.has_valid_headers(self.emissions_data))
 
+    def test_has_valid_headers_success_with_empty_file(self):
+        file_output = FileOutput("test.csv", self.temp_dir)
+        with open(file_output.save_file_path, "w", newline="") as _:
+            pass
+
+        self.assertTrue(file_output.has_valid_headers(self.emissions_data))
+
     def test_has_valid_headers_failure(self):
         file_output = FileOutput("test.csv", self.temp_dir)
         file_output.out(self.emissions_data, MagicMock())