How to mock method returning object using CppUTest

Question

I've following method:

QMap<QString, int> DefaultConfig::getConfig()
{
    QMap<QString, int> result;
    result.insert("Error", LOG_LOCAL0);
    result.insert("Application", LOG_LOCAL1);
    result.insert("System", LOG_LOCAL2);
    result.insert("Debug", LOG_LOCAL3);
    result.insert("Trace", LOG_LOCAL4);
    return result;
}

an I try to write mock which can return QMap prepared in test:

QMap<QString, int> DefaultConfig::getConfig() {
    mock().actualCall("getConfig");
    return ?
}

but I don't know how to mock the return value? I would like to use the mock in following way in TEST function:

QMap<QString, int> fake_map;
fake_map.insert("ABC", 1);
mock().expectOneCall("getConfig").andReturnValue(fake_map);

I cannot find such example in CppUTest Mocking documentation. I also know that .andReturnValue in this form will also not work.

ollo · Accepted Answer · 2016-07-22 19:35:55Z

Instead of passing the object by-value / -reference, pass by-pointer.

Example:

_{(I'm using an std::map here – QMap is exactly the same)}

Mock

You get the return value for the mock by the return#####Value() methods. Since returnPointerValue() returns a void* you have to cast it to proper pointer type. Then you can return by-value by dereferencing that pointer.

std::map<std::string, int> getConfig()
{
    auto returnValue = mock().actualCall("getConfig")
                                .returnPointerValue();
    return *static_cast<std::map<std::string, int>*>(returnValue);
}

Test

The expected return value is passed by pointer:

TEST(MapMockTest, mockReturningAMap)
{
    std::map<std::string, int> expected = { {"abc", 123} };
    mock().expectOneCall("getConfig").andReturnValue(&expected);

    auto cfg = getConfig();
    CHECK_EQUAL(123, cfg["abc"]);
}

Please not, there's a difference between Pointer and ConstPointer.

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