Testing Class Material

extra_slides/mocking/telescope/telescope_driver.py

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+
+def connect(address):
+    import time
+    time.sleep(5)
+    return '1'
+
+def get_angle(address):
+    return 0.0
+
+def set_angle(address, angle):
+    if angle < 0 or angle > 1.40:
+        raise IOError('Telescope jammed -- please call technical support')
+    return True

extra_slides/mocking/telescope/telescope_model.py

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+import telescope_driver
+
+
+class TelescopeModel(object):
+
+    # Minimum safe elevation angle (see handbook).
+    MIN_ANGLE = 0.0
+
+    # Maximum safe elevation angle (see handbook).
+    MAX_ANGLE = 80.0
+
+    def __init__(self, address):
+        self.address = address
+        # Connect to telescope
+        self.connection = telescope_driver.connect(address)
+        # Get initial state of telescope.
+        self.current_angle = telescope_driver.get_angle(self.connection)
+
+    def set_elevation_angle(self, angle):
+        """ Set the elevation angle of the telescope (in rad).
+
+        If the angle is outside the range allowed by the manufacturer,
+        raise a ValueError.
+        """
+
+        if angle < self.MIN_ANGLE or angle > self.MAX_ANGLE:
+            raise ValueError('Unsafe elevation angle: {}'.format(angle))
+
+        telescope_driver.set_angle(self.connection, angle)
+        self.current_angle = angle

extra_slides/mocking/telescope/test_telescope_model.py

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+import numpy as np
+from py.test import raises
+
+from telescope_model import TelescopeModel
+
+
+def test_unsafe_elevation_angle():
+    telescope = TelescopeModel(address='10.2.1.1')
+    elevation_angle = np.pi / 2.0
+
+    with raises(ValueError):
+        telescope.set_elevation_angle(elevation_angle)

extra_slides/mocking/telescope/test_telescope_model_with_mock.py

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+from unittest import mock
+
+import numpy as np
+from py.test import raises
+
+from telescope_model import TelescopeModel
+
+
+def test_unsafe_elevation_angle():
+    with mock.patch('telescope_model.telescope_driver'):
+        telescope = TelescopeModel(address='10.2.1.1')
+        elevation_angle = np.pi / 2.0
+        with raises(ValueError):
+            telescope.set_elevation_angle(elevation_angle)
+
+
+def test_model_initialization():
+    connection_id = 'bogus_connection'
+    initial_angle = 1.23
+
+    with mock.patch('telescope_model.telescope_driver') as driver:
+        driver.connect.return_value = connection_id
+        driver.get_angle.return_value = initial_angle
+
+        telescope = TelescopeModel(address='10.2.1.1')
+        assert telescope.connection == connection_id
+        assert driver.connect.call_count == 1
+        assert telescope.current_angle == initial_angle
+