Add tests for base Operation

Add unittests for the base class Operation. The tests focus on the static
factory method. This method has already been implemented.

doxec/tests/operation.py

+
+import unittest
+
+from doxec import Operation
+
+class ToyOperationA(Operation):
+    """
+    This toy operation is need for the unittests.
+    """
+    command = "op_a"
+    def execute(self):
+        pass
+
+class ToyOperationB(Operation):
+    """
+    This toy operation is need for the unittests.
+    """
+    command = "op_b"
+    def execute(self):
+        pass
+
+Operation.op_store.append(ToyOperationA)
+Operation.op_store.append(ToyOperationB)
+
+class OperationTestCase(unittest.TestCase):
+    """
+    Test case for the case class of all operations. The tests focus on the
+    factory facility. The Operation factory should know about the two toy
+    operations op_a and op_b.
+    """
+
+    def test_factory_op_a(self):
+        """
+        Test the factory when called with "op_a".
+        """
+        op_obj = Operation.factory("op_a", "args", "content")
+
+        self.assertIsInstance(op_obj, ToyOperationA)
+        self.assertEqual(op_obj.args, "args")
+        self.assertEqual(op_obj.content, "content")
+
+    def test_factory_op_b(self):
+        """
+        Test the factory when called with "op_b".
+        """
+        op_obj = Operation.factory("op_b", "args", "content")
+
+        self.assertIsInstance(op_obj, ToyOperationB)
+        self.assertEqual(op_obj.args, "args")
+        self.assertEqual(op_obj.content, "content")
+
+    def test_factory_unknown(self):
+        """
+        Test the factory when called with "op_c".
+        """
+        op_obj = Operation.factory("op_c", "args", "content")
+        self.assertIsNone(op_obj)
+
+
+