Added two unit tests for the format string datahandler + fix on a slicing end value

lodel/leapi/datahandlers/datas.py

@@ -26,7 +26,7 @@ build its content'
             datas[fname] for fname in self._field_list)
         if len(ret) > self.max_length:
             warnings.warn("Format field overflow. Truncating value")
-            ret = ret[:self.max_length-1]
+            ret = ret[:self.max_length]
         return ret
     
 ##@brief Varchar validated by a regex

tests/datahandlers/test_formatstring.py

@@ -0,0 +1,28 @@
+import unittest
+
+from lodel.leapi.datahandlers.datas import FormatString
+from lodel.editorial_model.components import EmClass
+
+
+class FormatStringTestCase(unittest.TestCase):
+
+    def test_construct_data(self):
+        test_class = EmClass('testing',display_name='testing class')
+        test_class.new_field('field1', 'varchar')
+        test_class.new_field('field2', 'varchar')
+
+        test_formatstring = FormatString('%s_%s',['field1', 'field2'], max_length=10)
+        formatted_string_value = test_formatstring.construct_data(test_class, 'field', {'field1': 'o'*5, 'field2': 'k'*4}, '')
+        self.assertEqual('%s_%s' % ('o'*5, 'k'*4), formatted_string_value)
+
+    def test_construct_too_long_data(self):
+        test_class = EmClass('testing', display_name='testing class')
+        test_class.new_field('field1', 'varchar')
+        test_class.new_field('field2', 'varchar')
+        test_formatstring = FormatString('%s-%s', ['field2', 'field1'], max_length=10)
+        formatted_string_value = test_formatstring.construct_data(test_class, 'field', {'field1': 'o'*300, 'field2': 'k'*500},'')
+        test_value = '%s-%s' % ('k'*500, 'o'*300)
+        self.assertNotEqual(test_value, formatted_string_value)
+        self.assertTrue(formatted_string_value in test_value)
+        self.assertTrue(len(formatted_string_value) == test_formatstring.max_length)
+        self.assertEqual(formatted_string_value, test_value[:test_formatstring.max_length])