update and test behaviour of dump_to_file

piqueserver/config.py

@@ -79,7 +79,7 @@ def get_dict(self):
 
     def load_from_file(self, fobj, format_=DEFAULT_FORMAT):
         '''
-        Clear the current configuration and load new configuration from a file like object
+        Clear the current configuration and load new configuration from a file-like object
         in a supported format.
         '''
         self._raw_config = {}
@@ -113,18 +113,17 @@ def update_from_dict(self, config):
         self._raw_config = self._nested_update(self._raw_config, config)
         self._validate_all()
 
-    def dump_to_file(self, out_file, format_=DEFAULT_FORMAT):
+    def dump_to_file(self, fobj, format_=DEFAULT_FORMAT):
         '''
-        Writes the current configuration to a file (filename specified by `out_file`),
+        Writes the current configuration to a file-like objection,
         with the format specified by `format_`.
         '''
-        with open(out_file, 'w') as f:
-            if format_ == TOML_FORMAT:
-                toml.dump(self._raw_config, f)
-            elif format_ == JSON_FORMAT:
-                json.dump(self._raw_config, f, indent=2)
-            else:
-                raise ValueError('Unsupported config file format: {}'.format(format_))
+        if format_ == TOML_FORMAT:
+            toml.dump(self._raw_config, fobj)
+        elif format_ == JSON_FORMAT:
+            json.dump(self._raw_config, fobj, indent=2)
+        else:
+            raise ValueError('Unsupported config file format: {}'.format(format_))
 
     def _get(self, name, default=None):
         if name not in self._raw_config:

tests/piqueserver/test_config.py

@@ -1,3 +1,5 @@
+import tempfile
+
 import unittest
 from piqueserver.config import config, JSON_FORMAT, TOML_FORMAT
 
@@ -168,3 +170,26 @@ def test_nested_update(self):
         self.assertEqual(raw['server']['things']['thing1'], 'something')
         self.assertEqual(raw['server']['things']['thing2'], 'added')
         self.assertEqual(raw['server']['name'], 'piqueserver instance')
+
+    def test_dump_to_file(self):
+        f = 'tests/example_config/simple.toml'
+        config.load_from_file(open(f))
+
+        with self.assertRaises(ValueError):
+            config.dump_to_file(None, format_='garbage123')
+
+        with tempfile.TemporaryFile(mode='w+') as f:
+            config.dump_to_file(f, JSON_FORMAT)
+            f.seek(0)
+            out = f.read().strip()
+            # at least make sure it wrote something that could be json
+            self.assertEqual(out[0], '{')
+            self.assertEqual(out[-1], '}')
+
+
+        with tempfile.TemporaryFile(mode='w+') as f:
+            config.dump_to_file(f, TOML_FORMAT)
+            f.seek(0)
+            out = f.read().strip()
+            # at least make sure it wrote something that could be toml
+            self.assertIn('[server]', out)