Use a mock keyring backend

Closes #2

Pipfile

@@ -1,20 +1,28 @@
 [[source]]
+
 url = "https://pypi.org/simple"
 verify_ssl = true
 name = "pypi"
 
+
 [packages]
+
 keyring = "*"
 ipython = "*"
 
+
 [dev-packages]
+
 pytest = "*"
 bumpversion = "*"
 sphinx = "*"
 sphinx-rtd-theme = "*"
 tox = "*"
 flit = "*"
 ipython = "*"
+pytest-watch = "*"
+
 
 [requires]
+
 python_version = "3.6"

conftest.py

@@ -0,0 +1,35 @@
+import os
+import keyring
+import pytest
+from keyring.errors import PasswordDeleteError
+
+os.environ['USER'] = 'ipython_secrets_PYTEST_USER'
+
+
+class MockKeyringBackend(keyring.backend.KeyringBackend):
+    _passwords = dict()
+
+    def clear(self):
+        self._passwords.clear()
+
+    def get_password(self, servicename, username):
+        return self._passwords.get((servicename, username))
+
+    def set_password(self, servicename, username, password):
+        self._passwords[(servicename, username)] = password
+
+    def delete_password(self, servicename, username):
+        try:
+            self._passwords.pop((servicename, username))
+        except IndexError:
+            raise PasswordDeleteError()
+
+
+mockKeyringBackend = MockKeyringBackend()
+keyring.set_keyring(mockKeyringBackend)
+
+
+@pytest.fixture
+def keyring_backend():
+    mockKeyringBackend.clear()
+    return mockKeyringBackend