test(test_date.py): add tests for negative timestamp evaluation

tests/test_date.py

@@ -726,6 +726,34 @@ def test_timestamp_in_microseconds(self):
             datetime.fromtimestamp(1570308760).replace(microsecond=263111)
         )
 
+    @parameterized.expand([
+        param(
+            input_timestamp='-1570308760',
+            negative_allowed=True,
+            result=datetime.fromtimestamp(-1570308760)
+        ),
+        param(
+            input_timestamp='-1570308760',
+            negative_allowed=False,
+            result=None
+        ),
+        param(
+            input_timestamp='1570308760',
+            negative_allowed=True,
+            result=None
+        ),
+        param(
+            input_timestamp='1570308760',
+            negative_allowed=False,
+            result=datetime.fromtimestamp(1570308760)
+        )
+    ])
+    def test_timestamp_with_negative(self, input_timestamp, negative_allowed, result):
+        self.assertEqual(
+            date.get_date_from_timestamp(input_timestamp, None, negative=negative_allowed),
+            result
+        )
+
     @parameterized.expand([
         param(date_string='15703087602631'),
         param(date_string='157030876026xx'),