[SOLVED] How to inspect argument to a gmock EXPECT

How to inspect argument to a gmock EXPECT_CALL()?

I'm using Google Mock (gMock) for the first time. Given the following code snippet:

class LinkSignals
{
    public:
        virtual ~LinkSignals() { }

        virtual void onLink(std::string) = 0;
        virtual void onUnLink() = 0;
};


class MockLinkSignals : public LinkSignals
{
    public:
        MOCK_METHOD1(onLink, void(std::string));
        MOCK_METHOD0(onUnLink, void());
};

MockLinkSignals mock_signals;

When I execute some test code that causes EXPECT_CALL(mock_signals, onLink(_)) to be run how can I inspect the argument to onLink()?

Solution

You would normally use either existing gmock matchers or define your own to check the arguments passed to the mock method.

For example, using the default Eq equality matcher:

EXPECT_CALL(mock_signals, onLink("value_I_expect"))

Or check for sub string say:

EXPECT_CALL(mock_signals, onLink(HasSubstr("contains_this")))

The gmock documentation provides details of the standard matchers that are available, and also describes how to make custom matchers, for example for an integer argument type:

MATCHER(IsEven, "") { return (arg % 2) == 0; }

It is possible to capture an argument to a variable by attaching an action to the expectation, although this can have limited use in the scope of the expectation:

EXPECT_CALL(mock_signals, onLink(_)).WillOnce(SaveArg<0>(pointer))

I'd suggest studying the various matchers and actions available before choosing the best approach for your particular case.