Add retrieve method for Source

omise/__init__.py

@@ -1749,12 +1749,27 @@ class Source(_MainResource, Base):
         )
     """
 
+    @classmethod
+    def _instance_path(cls, source_id):
+        return ('sources', source_id)
+
     @classmethod
     def create(cls, **kwargs):
         return _as_object(
             cls._request('post',
                          'sources', kwargs))
 
+    @classmethod
+    def retrieve(cls, source_id):
+        """Retrieve the source details for the given :param:`source_id`.
+
+        :param source_id: a source id to retrieve.
+        :type source_id: str
+        :rtype: Source
+        """
+        return _as_object(
+            cls._request('get',
+                         cls._instance_path(source_id)))
 
 class Transfer(_MainResource, Base):
     """API class representing a transfer.

omise/test/test_source.py

@@ -79,3 +79,27 @@ def test_create_offline(self, api_call):
                 'type': 'tesco_lotus'
             }
         )
+
+    @mock.patch('requests.get')
+    def test_retrieve(self, api_call):
+        class_ = self._getTargetClass()
+        self.mockResponse(api_call, """{
+            "object": "source",
+            "id": "src_test",
+            "type": "internet_banking_test",
+            "flow": "redirect",
+            "amount": 100000,
+            "currency": "thb"
+        }""")
+
+        source = class_.retrieve('src_test')
+        self.assertTrue(isinstance(source, class_))
+        self.assertEqual(source.id, 'src_test')
+        self.assertEqual(source.type, 'internet_banking_test')
+        self.assertEqual(source.flow, 'redirect')
+        self.assertEqual(source.amount, 100000)
+        self.assertEqual(source.currency, 'thb')
+        self.assertRequest(
+            api_call,
+            'https://api.omise.co/sources/src_test'
+        )