Looking for syntax to return a copy of const std::string as std::string from mock

[David Wallace]

Using Gmock 1.6 with Visual Studio 2013 on Windows:

The method I am trying to mock has signature:

virtual std::string translate_sdc_name_interface(const std::string& name, const std::string &  hierDelimiter, drModuleInst * topModule) const = 0;

The corresponding mock declaration is:

  MOCK_CONST_METHOD3(translate_sdc_name_interface,

      std::string(const std::string& name, const std::string & hierDelimiter, drModuleInst * topModule));

When the mocked method is invoked, I want the default action to be to return a copy of the first argument.  None of the following syntaxes work:

class StructVendorOptionsTest : public VendorOptionsTest {

public:

StructVendorOptionsTest() {

//ON_CALL(vendorExterns, translate_sdc_name_interface(_, _, _)).WillByDefault(ReturnArg<0>);

//ON_CALL(vendorExterns, translate_sdc_name_interface(_, _, _)).WillByDefault(WithArg<0>(ReturnNew<std::string>));

//ON_CALL(vendorExterns, translate_sdc_name_interface(_, _, _)).WillByDefault(WithArg<0>(ReturnNew<std::string>()));

//ON_CALL(vendorExterns, translate_sdc_name_interface(_, _, _)).WillByDefault(ReturnNew<std::string>(ReturnArg<0>()));

}

protected:

MockVendorExterns vendorExterns;

};

The first of these complains about being unable to convert a const std::string & to a std::string; the others result in various syntax errors with the template expansions. I haven't found a good example of this in the documentation. What's the right syntax to use here (I assume it is possible to do this)?

Dave W.

[David Wallace]

I've now found that I can use an explicit helper function to get the result I want.  But is there a cleaner way to do this that doesn't require the helper function?

static std::string CopyString(const std::string &arg) { return arg; }

class StructVendorOptionsTest : public VendorOptionsTest {

public:

StructVendorOptionsTest() {

//ON_CALL(vendorExterns, translate_sdc_name_interface(_, _, _)).WillByDefault(ReturnArg<0>);

//ON_CALL(vendorExterns, translate_sdc_name_interface(_, _, _)).WillByDefault(WithArg<0>(ReturnNew<std::string>));

//ON_CALL(vendorExterns, translate_sdc_name_interface(_, _, _)).WillByDefault(WithArg<0>(ReturnNew<std::string>()));

//ON_CALL(vendorExterns, translate_sdc_name_interface(_, _, _)).WillByDefault(ReturnNew<std::string>(ReturnArg<0>()));

ON_CALL(vendorExterns, translate_sdc_name_interface(_, _, _)).WillByDefault(WithArg<0>(Invoke(CopyString)));

}

protected:

MockVendorExterns vendorExterns;

};

[Samuel Benzaquen]

Can you post the full compiler output of the 'ReturnArg<0>' version?

That seems like it should work.

_Sam

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[David Wallace]

Hi, Samuel.  When I uncomment the first line (with ReturnArg<0>), the compiler output I get is:

2>------ Build started: Project: Test_Shared_SDCVendorOptions_SDCVendorOptions, Configuration: Debug Win32 ------

2>  TestSDCVendorOptions.cpp

2>c:\users\dave\documents\visual studio 2008\projects\clocks\shared\sdcvendoroptions\unittests\testsdcvendoroptions.cpp(305): error C2664: 'testing::internal::OnCallSpec<F> &testing::internal::OnCallSpec<F>::WillByDefault(const testing::Action<F> &)' : cannot convert argument 1 from 'testing::ReturnArgAction<k> (__cdecl *)(void)' to 'const testing::Action<F> &'

2>          with

2>          [

2>              F=std::string (const std::basic_string<char,std::char_traits<char>,std::allocator<char>> &,const std::basic_string<char,std::char_traits<char>,std::allocator<char>> &,drModuleInst *)

2>          ]

2>          Reason: cannot convert from 'overloaded-function' to 'const testing::Action<F>'

2>          with

2>          [

2>              F=std::string (const std::basic_string<char,std::char_traits<char>,std::allocator<char>> &,const std::basic_string<char,std::char_traits<char>,std::allocator<char>> &,drModuleInst *)

2>          ]

2>          No constructor could take the source type, or constructor overload resolution was ambiguous

(Note: the path to my source files goes through a visual studio 2008 directory, but the current compiler being used is visual studio 2013.)  I hope this is helpful.

Dave W.

[Samuel Benzaquen]

I see the problem now. I missed it when I first read your code.

ReturnArg<> is a function that returns an action. You must call it. It should be: WillByDefault(ReturnArg<0>())

Note that ReturnNew<> is also a function that returns an action.

_Sam

[David Wallace]

Thanks, Samuel.  That was indeed the problem.  It can be challenging to interpret template error messages involving code you didn't write - in this case, I saw the error involving inability to convert something involving the const string reference, and drew the wrong conclusion from it.

Dave W.