Google test save one argument into another argument

Question

Is possible to save one argument from a mock function call into another ? for instance argument 1 into argument 4 ?

EXPECT_CALL(mock_, up_func(_, _, _, _)).
.WillOnce(DoAll(SaveArg<1>(Argument4), Return(LSUCCESS)));

Answer 1

You can do that either with Invoke

EXPECT_CALL(mock_, up_func(_, _, _, _))
.WillOnce(
    WithArgs<0, 3>(
        Invoke([](auto in, auto& out){out = in; return LSUCCESS;})
    )
 );

Or using a helper variable

int helper;
EXPECT_CALL(mock_, up_func(_, _, _, _))
.WillOnce(
    DoAll(
        SaveArg<0>(&helper),
        SetArgReferee<3>(ByRef(helper)),
        Return(0)
    )
 );

Note: ByRef is important, otherwise you will get copy of the value of helper from the moment when expectation was set, not the value set later by SaveArg.

A third option would be to define a custom action if this is something you will be using a lot. Custom action could be used with WithArgs to select arguments (simpler version) or templated to avoid WithArgs everytime (harder).

See it online