Unit tests for FunctionNow

Author: mzinin

test/functions/test_function_now.py

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+from s2e2.error import ExpressionError
+from s2e2.functions.function_now import FunctionNow
+
+import datetime
+import pytest
+
+
+class TestFunctionNow:
+
+    def setup_class(self):
+        self.function = FunctionNow()
+
+
+    def teardown_class(self):
+        self.function = None
+
+
+    def test_positive_stack_size(self):
+        stack = []
+        self.function.invoke(stack)
+        assert len(stack) == 1
+
+
+    def test_positive_result_type(self):
+        stack = []
+        self.function.invoke(stack)
+        assert isinstance(stack[0], datetime.datetime)
+
+
+    def test_positive_result_value(self):
+        stack = []
+        self.function.invoke(stack)
+
+        now = datetime.datetime.utcnow()
+        function_result = stack[0]
+        MAX_DIFF_IN_SECONDS = 2
+
+        assert now >= function_result
+        assert (now - function_result).seconds < MAX_DIFF_IN_SECONDS
+
+
+    def test_positive_more_arguments_stack_size(self):
+        stack = [False, 'A', 'B']
+        self.function.invoke(stack)
+        assert len(stack) == 4