Googlemock: How to verify elements in an array in an object?

Question

I have a small class:

struct Command
{
    uint8_t cmdId;
    uint8_t len;
    uint8_t payload[MAX_PAYLOAD];
};

And I want to verify only the first two elements of the payload using a googlemock expectation. I can't use ElementsAreArray because that checks that the lengths of the payload and the expectation are the same. So far I have an expectation that looks like this:

Command cmd;
cmd.cmdId = 0xD3;
cmd.len = 2;
cmd.payload[0] = 'm';
cmd.payload[1] = 'l';

EXPECT_CALL(mockQueue,
        sendFromIsr(Pointee(AllOf(
                Field(&Command::cmdId, Eq(0xD3)),
                Field(&Command::len, Eq(2)),
                //Field(&BirdCommand::payload, ElementsAreArray(cmd.payload, 2)) !<-- Doesn't work
        ))))
        .WillOnce(Return(true));

Any ideas? The mock class looks like this:

template <typename T>
class MockQueue : public Queue<T>
{
public:
    MOCK_METHOD1_T(sendFromIsr, bool(T &item));
};

Answer 1

I have received this solution from Piotr Gorak via the googlemock mailing list, discussion here.

MATCHER_P2(CheckFirstTwo, first, second, "Checks the first two elements of an array")
{
    return arg[0] == first && arg[1] == second;
}

And in the test I verify like this:

EXPECT_CALL(mockQueue, sendFromIsr(
        Pointee(AllOf(
            Field(&BirdCommand::cmdId, Eq(0xD3)),
            Field(&BirdCommand::len, Eq(2)),
            Field(&BirdCommand::payload, CheckFirstTwo('m', 'l'))
        ))
));

I like this solution the most because it does not require me to over-specify the test or zero initialize the data structure in my production code unnecessarily.

Answer 2

What is wrong with this :

EXPECT_CALL( mockQueue, sendFromIsr( Ref( cmd ) )
        .WillOnce( Return( true ) );

?

Since the Command is POD, it should work even if it copies the command (which it doesn't in this case).

---

EDIT

Since the Command is POD, you need to zero initialize it (or clear the memory occupied by such object when you create it. In your example :

Command cmd = Command();

Then your object will not be uninitialized and the comparison should not fail.

Answer 3

Have you tried

EXPECT_CALL(mockQueue,
        sendFromIsr(Pointee(AllOf(
                Field(&Command::cmdId, Eq(0xD3)),
                Field(&Command::len, Eq(2)),
                Field(&Command::payload[0], Eq('m')),
                Field(&Command::payload[1], Eq('l'))
        ))))
        .WillOnce(Return(true));