FIX: remove wrong tests in test_value.cpp

test/test_value.cpp

@@ -153,30 +153,24 @@ TEST(test_value, test_abstract_value) {
     vals.push_back(num);
   }
   Value value(vals);
-  EXPECT_EQ("", value.ToString());
   EXPECT_TRUE(value.IsVector());
 
   AbstractValue *abstract_value = &value;
-  EXPECT_EQ("", abstract_value->ToString());
   EXPECT_TRUE(abstract_value->IsVector());
 
   Value value2(*abstract_value);
-  EXPECT_EQ("", value2.ToString());
   EXPECT_TRUE(value2.IsVector());
 
   ScalarValue scalar_value = value.GetAsVector().at(2);
   EXPECT_TRUE(scalar_value.IsDouble());
-  EXPECT_EQ("", scalar_value.ToString());
   EXPECT_EQ(scalar_value.GetAsDouble(), 27.5);
 
   AbstractValue *abstract_scalar_value = &scalar_value;
-  EXPECT_EQ("", abstract_scalar_value->ToString());
   EXPECT_TRUE(abstract_scalar_value->IsDouble());
   EXPECT_EQ(abstract_scalar_value->GetAsDouble(), 27.5);
 
   Value scalar_value2(*abstract_scalar_value);
   EXPECT_TRUE(scalar_value2.IsDouble());
-  EXPECT_EQ("", scalar_value2.ToString());
   EXPECT_EQ(scalar_value2.GetAsDouble(), 27.5);
 }