Fixed deprecated py.test funcargs example. Completed mock unit test example. Up Next: How much testing is enough?

dpitic · dpitic · commit de836492ae95 · 2017-01-06T20:52:34.000+08:00
diff --git a/ch12/funcargs_pytest.py b/ch12/funcargs_pytest.py
@@ -1,16 +1,18 @@
 from stats import StatsList
+import pytest
 
 """
-Demonstration of using the py.test funcargs feature to set up variables.
+Demonstration of using the py.test framework @pytest.fixture() feature to set up
+variables.
 """
 
 
-def pytest_funcarg__valid_stats(request):
+#def pytest_funcarg__valid_stats(request):  # this is deprecated
+@pytest.fixture
+def valid_stats(request):
     """
     Global test configuration. This function can also be placed in conftest.py
-    which is parsed by py.test. Funcargs must be named according to the
-    convention pytest_funcarg__<identifier>, where <identifier> is a valid
-    variable name that can be used as a parameter in a test function.
+    which is parsed by py.test.
     :param request:
     :return: object to be passed as an argument into the individual test
     functions.
diff --git a/ch12/mock_flightstatus.py b/ch12/mock_flightstatus.py
@@ -0,0 +1,74 @@
+import datetime
+import redis
+import pytest
+from unittest.mock import Mock
+from unittest.mock import patch
+
+"""
+Demonstration of mocking in unit testing using unittest.mock standard library.
+
+The Mock() class removes the need to create stubs throughout the test suite.
+After performing any action, assertions can be made about which methods or
+attributes were used and the arguments they were called with.
+"""
+
+
+class FlightStatusTracker:
+    """
+    This class is responsible for tracking flight statuses in a key-value store
+    so that the timestamp and the most recent status can be stored.
+    """
+    ALLOWED_STATUSES = {'CANCELLED', 'DELAYED', 'ON TIME', 'ARRIVED'}
+
+    def __init__(self, redis_instance=None):
+        self.redis = redis_instance if redis_instance else redis.StrictRedis()
+
+    def change_status(self, flight, status):
+        status = status.upper()
+        if status not in self.ALLOWED_STATUSES:
+            raise ValueError('{} is not a valid status'.format(status))
+
+        key = 'flightno:{}'.format(flight)
+        value = '{}|{}'.format(datetime.datetime.now().isoformat(), status)
+        self.redis.set(key, value)      # This should be tested
+
+
+@pytest.fixture
+def tracker():
+    return FlightStatusTracker()
+
+
+def test_mock_method(tracker):
+    """
+    Test that the flight status is not valid and that it was not set in the
+    database.
+    :param tracker: FlightStatusTracker object under test.
+    :return: None
+    """
+    tracker.redis.set = Mock()  # create mock object for the redis.set() method
+    with pytest.raises(ValueError) as ex:
+        tracker.change_status('AC101', 'lost')
+    assert ex.value.args[0] == 'LOST is not a valid status'
+    assert tracker.redis.set.call_count == 0
+
+
+def test_patch(tracker):
+    """
+    Demonstration of the unittest.mock.patch() method used to mock the standard
+    library datetime object.
+    :param tracker: FlightStatusTracker object under test.
+    :return: None
+    """
+    tracker.redis.set = Mock()
+    # Create a known datetime for test purposes
+    fake_now = datetime.datetime(2015, 4, 1)
+    # Mock the standard library datetime to return the known test value
+    with patch('datetime.datetime') as dt:
+        dt.now.return_value = fake_now
+        tracker.change_status('AC102', 'on time')
+    dt.now.assert_called_once_with()    # Make sure the datetime.now() is called
+    # Make sure the redis mock object was called with the correct parameters
+    tracker.redis.set.assert_called_once_with(
+        'flightno:AC102',
+        '2015-04-01T00:00:00|ON TIME'
+    )
