#150: Add findone tests for DB backend

- This commit also includes a fixes a bug found on the 404 of that test class

datagateway_api/common/database/helpers.py

@@ -329,7 +329,11 @@ def get_first_filtered_row(table, filters):
     :return: the first row matching the filter
     """
     log.info(" Getting first filtered row for %s", table.__tablename__)
-    return get_rows_by_filter(table, filters)[0]
+    try:
+        result = get_rows_by_filter(table, filters)[0]
+    except IndexError:
+        raise MissingRecordError()
+    return result
 
 
 def get_filtered_row_count(table, filters):

test/db/endpoints/test_findone_db.py

@@ -0,0 +1,25 @@
+class TestDBFindone:
+    def test_valid_findone_with_filters(
+        self,
+        flask_test_app_db,
+        valid_db_credentials_header,
+        single_investigation_test_data_db,
+    ):
+        test_response = flask_test_app_db.get(
+            '/investigations/findone?where={"TITLE": {"like": "Title for DataGateway'
+            ' API Testing (DB)"}}',
+            headers=valid_db_credentials_header,
+        )
+
+        assert test_response.json == single_investigation_test_data_db.to_dict()
+
+    def test_valid_no_results_findone_with_filters(
+        self, flask_test_app_db, valid_db_credentials_header,
+    ):
+        test_response = flask_test_app_db.get(
+            '/investigations/findone?where={"TITLE": {"eq": "This filter should cause a'
+            '404 for testing purposes..."}}',
+            headers=valid_db_credentials_header,
+        )
+
+        assert test_response.status_code == 404

test/icat/endpoints/test_findone_icat.py

@@ -1,7 +1,7 @@
 from test.icat.test_query import prepare_icat_data_for_assertion
 
 
-class TestFindone:
+class TestICATFindone:
     def test_valid_findone_with_filters(
         self,
         flask_test_app_icat,