Fixed bug in json formatter (#190)

Closes #189 

Fixed bug, and added a pytest since there wasn't one

src/regtech_data_validator/data_formatters.py

@@ -108,10 +108,11 @@ def df_to_json(df: pd.DataFrame) -> str:
     # for tying those objects back together.  Grouping adds a little more processing
     # time for smaller datasets but keeps really larger ones from crashing.
     json_results = []
-    grouped_df = df.groupby('validation_id')
-    for group_name, group_data in grouped_df:
-        json_results.append(process_chunk(group_data, group_name))
-    json_results = sorted(json_results, key=lambda x: x['validation']['id'])
+    if not df.empty:
+        grouped_df = df.groupby('validation_id')
+        for group_name, group_data in grouped_df:
+            json_results.append(process_chunk(group_data, group_name))
+        json_results = sorted(json_results, key=lambda x: x['validation']['id'])
     return ujson.dumps(json_results, indent=4, escape_forward_slashes=False)
 
 

tests/test_output_formats.py

@@ -1,4 +1,5 @@
 import pandas as pd
+import ujson
 
 from regtech_data_validator.data_formatters import df_to_csv, df_to_str, df_to_json, df_to_table, df_to_download
 from regtech_data_validator.checks import Severity
@@ -85,6 +86,12 @@ def test_output_csv(self):
         actual_output = df_to_csv(self.input_df)
         assert actual_output.strip('\n') == expected_output
 
+    def test_empty_results_json(self):
+        expected_output = ujson.dumps([], indent=4, escape_forward_slashes=False)
+        actual_output = df_to_json(pd.DataFrame())
+
+        assert actual_output == expected_output
+
     def test_output_json(self):
         expected_output = dedent(
             """