create test for #4 (~/.dockercfg writing)

tests/test_api.py

@@ -1,10 +1,12 @@
+import json
 import os
 from mock import MagicMock
 import yaml
 from pierone.api import docker_login
 
 
-def test_docker_login(monkeypatch):
+def test_docker_login(monkeypatch, tmpdir):
+    monkeypatch.setattr('os.path.expanduser', lambda x: x.replace('~', str(tmpdir)))
     response = MagicMock()
     response.json.return_value = {'access_token': '12377'}
     monkeypatch.setattr('requests.get', MagicMock(return_value=response))
@@ -16,3 +18,27 @@ def test_docker_login(monkeypatch):
     assert {'auth': 'b2F1dGgyOjEyMzc3', 'email': 'no-mail-required@example.org'} == data.get('https://pierone.example.org')
 
 
+def test_keep_dockercfg_entries(monkeypatch, tmpdir):
+    monkeypatch.setattr('os.path.expanduser', lambda x: x.replace('~', str(tmpdir)))
+    response = MagicMock()
+    response.json.return_value = {'access_token': '12377'}
+    monkeypatch.setattr('requests.get', MagicMock(return_value=response))
+    path = os.path.expanduser('~/.dockercfg')
+
+    key = 'https://old.example.org'
+    existing_data = {
+        key: {
+            'auth': 'abc123',
+            'email': 'jdoe@example.org'
+        }
+    }
+    with open(path, 'w') as fd:
+        json.dump(existing_data, fd)
+
+    token = docker_login('https://pierone.example.org', 'services', 'mytok',
+                         'myuser', 'mypass', 'https://token.example.org', use_keyring=False)
+    with open(path) as fd:
+        data = yaml.safe_load(fd)
+    assert {'auth': 'b2F1dGgyOjEyMzc3', 'email': 'no-mail-required@example.org'} == data.get('https://pierone.example.org')
+    assert existing_data.get(key) == data.get(key)
+