add zero attribute test for tanh op (#5427)

* add zero attribute test for tanh op

* apply review suggestion

Co-authored-by: Patryk Elszkowski <patryk.elszkowki@intel.com>

ngraph/test/CMakeLists.txt

@@ -258,6 +258,7 @@ set(SRC
     visitors/op/squeeze.cpp
     visitors/op/sqrt.cpp
     visitors/op/strided_slice.cpp
+    visitors/op/tanh.cpp
     visitors/op/topk.cpp
     visitors/op/transpose.cpp
     uint4.cpp

ngraph/test/visitors/op/tanh.cpp

@@ -0,0 +1,27 @@
+// Copyright (C) 2021 Intel Corporation
+// SPDX-License-Identifier: Apache-2.0
+//
+
+#include "gtest/gtest.h"
+
+#include "ngraph/ngraph.hpp"
+#include "ngraph/op/util/attr_types.hpp"
+#include "ngraph/opsets/opset1.hpp"
+
+#include "util/visitor.hpp"
+
+using namespace std;
+using namespace ngraph;
+using ngraph::test::NodeBuilder;
+
+TEST(attributes, tanh_op)
+{
+    NodeBuilder::get_ops().register_factory<op::Tanh>();
+    const auto data_node = make_shared<op::Parameter>(element::f32, Shape{1});
+    const auto tanh = make_shared<op::Tanh>(data_node);
+
+    const NodeBuilder builder(tanh);
+    const auto tanh_attr_number = 0;
+
+    EXPECT_EQ(builder.get_value_map_size(), tanh_attr_number);
+}